Internal latch release mechanism for externally-gripping casing running tools

ABSTRACT

A rotary latch release mechanism includes axially-aligned upper and lower rotary latch components carried on and rotationally coupled to upper and lower latch assemblies, respectively. The latch release mechanism is movable from an axially-latched position to an axially-unlatched position in response to relative rotation between the upper and lower rotary latch components. The latch release mechanism has a movable land surface that acts in response to relative axial displacement to induce the relative rotation required to release the latch. The latch release mechanism may be configured such that the axial movement of the movable land surface will cause the relative axial movement required to release the latch in combination with the required rotation. Accordingly, the rotary latch mechanism operates in response to externally-controlled axial movement of a movable land surface carried by the latch release mechanism, without requiring externally-induced rotation.

FIELD

The present disclosure relates in general to devices and mechanisms for releasably latching two coaxially-positioned and mating rotary components such that relative axial displacement of the rotary components is prevented when in the latched position, but axial displacement is allowed when the rotary components are in the unlatched position.

BACKGROUND

Power tongs have for many years been used to “make up” (i.e., assemble) threaded connections between sections (or “joints”) of tubing, and to “break out” (i.e., disassemble) threaded connections when running tubing strings into or out of petroleum wells, in coordination with the hoisting system of a drilling rig. Tubing strings typically comprise a number of tubing sections having externally-threaded ends, joined end-to-end by means of internally-threaded cylindrical couplers mounted at one end of each tubing section, forming what is commonly called the “box” end, while the other externally-threaded end of the tubing section is called the “pin” end. Such tubular strings can be relatively efficiently assembled or disassembled using power tongs to screw additional tubing sections into a tubing string during make-up operations, or to unscrew tubing sections from a tubing string being pulled from a wellbore (i.e., break-out operations).

However, power tongs do not simultaneously support other beneficial functions such as rotating, pushing, or fluid filling, after a pipe segment is added to or removed from the string, and while the string is being lowered or raised in the wellbore. Running tubulars with tongs, whether powered or manual, also typically requires the deployment of personnel in comparatively high-hazard locations such as on the rig floor and on so-called “stabbing boards” above the rig floor.

The advent of drilling rigs equipped with top drives has enabled another method of running tubing strings, and casing strings in particular, using tools commonly known as casing running tools or CRTs. These tools are configured to be carried by the top drive quill, and to grip the upper end of a tubing section and to seal between the bore of the tubing section and the bore of the top drive quill. In coordination with the top drive, CRTs support hoisting, rotating, pushing, and filling of a casing string with drilling fluid while running casing into a wellbore.

Ideally, these tools also support make-up and break-out operations traditionally performed using power tongs, thereby eliminating the need for power tongs entirely, with attendant benefits in terms of reduced system complexity and increased safety. As a practical matter, however, obtaining these benefits without negatively impacting running rate or consistency requires the time taken to make up connections using CRTs to be at least comparable to that required for the running rate and consistency achievable using power tongs. In addition, it is a practical reality that making up tubing strings using CRTs does increase the risk of damage to the connection threads, or to seals in so-called “premium connections” where these are present.

U.S. Pat. No. 7,909,120 (Slack) [the contents of which are incorporated herein in their entirety] teaches a prior art CRT in the form of a gripping tool that includes a body assembly comprising:

-   -   a load adaptor coupled for axial load transfer to the remainder         of the body assembly, and adapted for structural connection to         either a drive head or a reaction frame;     -   a gripping assembly carried by the body assembly and having a         grip surface, wherein the gripping assembly is provided with         activating means to radially stroke or move the grip surface         from a retracted position to an engaged position in which the         grip surface tractionally engages either an interior surface or         an exterior surface of a tubular workpiece in response to         relative axial movement or axial stroke of the body assembly in         at least one direction relative to the grip surface; and     -   a linkage acting between the body assembly and the gripping         assembly, wherein relative rotation of the load adaptor in at         least one direction relative to the grip surface will result in         axial displacement of the body assembly relative to the gripping         assembly, so as to move the gripping assembly from the retracted         position to the engaged position in accordance with the action         of the actuation means.

For purposes of this patent document, a CRT configured for gripping an internal surface of a tubular workpiece will be referred to as a CRTi, and a CRT configured for gripping an external surface of a tubular workpiece will be referred to as a CRTe.

CRTs as taught by U.S. Pat. No. 7,909,120 utilize a mechanically-actuated gripping assembly that generates its gripping force in response to axial load with corresponding axial stroke, either together with or independently from externally-applied axial load and externally-applied torque load applied by either right-hand or left-hand rotation. These loads, when applied, are carried across the tool from the load adaptor of the body assembly to the grip surface of the gripping assembly, in tractional engagement with the workpiece.

Additionally, such CRTs or gripping tools may be provided with a latch mechanism acting between the body assembly and the gripping assembly, in the form of a rotary J-slot latch having a hook-and-receiver arrangement acting between first and second latch components, where the first latch component is carried by the body assembly and the second latch component is carried by the grip assembly (for example, see FIGS. 1 and 14 in U.S. Pat. No. 7,909,120, showing the latch in externally-gripping and internally-gripping full-tool assemblies respectively, and also FIGS. 4-7 in U.S. Pat. No. 7,909,120, describing how mating latch teeth 108 and 110 act as a hook and receiver with respect to each other).

When in a first (or latched) position, with the hook in the receiver, this latch prevents relative axial movement between the body assembly and the gripping assembly so as to retain the grip mechanism in a first (or retracted) position. However, relative rotation between the body assembly and the gripping assembly (which rotation is typically resisted by some amount of torque, which will be referred to herein as the “latch actuation torque”) will move the mating hook and receiver components to a second (or unlatched) position, thereby allowing relative axial movement between the body assembly and the gripping assembly, with associated movement of the grip surface into the second (or engaged) position. Accordingly, when in the latched position, this latch mechanism will support operational steps that require the gripping assembly to be held in its retracted position, to enable positioning of the tool relative to the workpiece preparatory to engaging the grip surface, and conversely retaining the grip surface in its retracted position enabling separation of the CRT from the workpiece.

Operationally, achieving this relative movement where the CRT is attached to the top drive quill requires the development of sufficient reaction torque, through tractional engagement when the “land surface” of the CRT is brought into contact with the upper end of a tubular workpiece and axial “set-down” force is applied, to resist the latch actuation torque arising from the rotation applied to move the latch into the unlatched position (typically arranged as right-hand rotation) and to cause axial movement if required (i.e., to move the hook up the “slot” of a J-slot). Any operational step moving the latch from the latched position to the unlatched position is said to “trigger” the tool, thus allowing the tool to be “set”.

To re-latch, this same requirement for sufficient tractional resistance between the tool's land surface and the workpiece must be met, with the applied torque direction reversed (i.e., typically left-hand rotation) to “un-set” the tool. For mechanically-set CRTs such as in U.S. Pat. No. 7,909,120, the tractional resistance required to re-latch is less than that required to unlatch.

U.S. Pat. No. 9,869,143 (Slack) [the contents of which are incorporated herein in their entirety, in jurisdictions where so permitted] discusses how it may be difficult in some applications to achieve sufficient tractional resistance between the land surface of a CRT and a workpiece, such as in cases where both the CRT land surface and the contact face of the workpiece are smooth steel, particularly when rotating to release the latch in such tools. U.S. Pat. No. 9,869,143 teaches means for increasing the effective friction coefficient acting between the workpiece and tool under application of compressive load (i.e., the ratio of tractional resistance to applied load). While these teachings disclose effective means for managing this operational variable and thus reducing operational uncertainty, operation of the tool still requires the steps of first setting down a somewhat controlled amount of axial load and then applying rotation with the top drive to move the latch into its unlatched position. Therefore, when the CRT is used to for make-up operations, the time, load, and rotation control to carry out these steps on certain rigs may result in slower cycle times than achievable using power tongs for make-up.

Tubing sections in a tubing string are typically oriented “pin down, box up”. Accordingly, during make-up operations, the upper end of the uppermost section in the string, as supported by rig floor slips or a “spider”, presents as “box up” in the so-called “stump” into which the pin end of the next tubing section (i.e., workpiece) is stabbed. When using a CRT for make-up, it may be difficult to control the amount of top drive “set-down” load on the stabbed pin and similarly the amount of rotation applied with set-down load present, introducing the possibility of the undesirable situation where the pin end of the workpiece is rotated in the box in the stump before the pin-end and box-end threads are properly engaged, with the attendant risk of galling damage to the threads. While these risks can be ameliorated by careful control of the top drive by the driller, they contribute to both additional uncertainty and increased cycle time.

Accordingly, there is a need for methods and means for reducing the risk of thread damage when using CRTs for make-up, and for providing greater assurance of cycle times comparable to or less than cycle times achievable using power tongs for make-up and other aspects of casing running operations.

SUMMARY OF THE DISCLOSURE

In general terms, the present disclosure teaches non-limiting embodiments of a rotary latch mechanism (alternatively referred to as a trigger mechanism) comprising upper and lower latch assemblies, plus a latch release mechanism comprising an upper rotary latch component carried on and rotationally coupled to the upper latch assembly, and a lower rotary latch component carried on and rotationally coupled to the lower latch assembly. The upper and lower rotary components are configured to move from a first (or axially-latched) position to a second (or axially-unlatched) position in response to rotation of the lower rotary component relative to the upper rotary component in a first (or unlatching) direction. Such rotation induces the development of an associated latch actuation torque.

The latch release mechanism has a movable land element (alternatively referred to as a “cushion bumper”) which carries a downward-facing land surface that acts in response to relative axial displacement to urge relative rotation between the upper and lower rotary latch components, so as to exert the latch actuation torque required to move the latch components from the latched position to the unlatched position. Where needed for latch configurations requiring both relative axial compression movement and rotation (such as commonly required for a J-slot latch), the mechanism may be configured such that the axial movement of the movable land element will cause the relative axial movement required to release the latch in combination with the required rotation. Accordingly, exemplary embodiments in accordance with the present teachings are directed to means for inducing the rotation and latch actuation torque required to move the component forming a rotary latch from the latched position to the unlatched position using externally-controlled axial movement of a movable land element carried by the latch release mechanism, without requiring externally-induced rotation sufficient to move the mechanism from the latched position to the unlatched position.

Latch release mechanisms as disclosed herein eliminate the need for externally-applied rotation after applying set-down force when using a tool such as a mechanical CRT that employs a J-latch type mechanism to move from a first (latched) to a second (unlatched) position, by transforming relative axial movement between the tubular workpiece and a component of the tool so as to produce the relative rotation needed to release the latch. This enables a mechanical CRT equipped with such a latch release mechanism (or trigger mechanism) to produce comparable or shorter cycle times with reduced risk of connection thread damage while running casing, as compared to using power tongs for such operations.

In one aspect, the present disclosure teaches embodiments of a rotary latch release mechanism comprising:

-   -   an upper latch assembly and a lower latch assembly, said upper         and lower latch assemblies being in axial alignment;     -   an upper rotary latch component carried on and rotationally         coupled to the upper latch assembly, and a lower rotary latch         component carried on and rotationally coupled to the lower latch         assembly;     -   a bumper element defining a downward-facing land surface, with         the bumper element being coupled to the lower latch assembly so         as to be both axially movable and rotationally movable relative         to the lower latch assembly; and     -   a trigger element coupled to the bumper element and the lower         latch assembly so as to be movable at least axially relative to         the bumper element, and so as to be axially and rotationally         movable relative to the lower latch assembly;         wherein:     -   the upper and lower rotary latch components are configured to         move from an axially-latched position to an axially-unlatched         position in response to relative rotation between the upper and         lower rotary latch components in a first rotational direction;     -   the upper latch assembly defines one or more downward-facing         trigger reaction dog pockets; and     -   the trigger element defines one or more upward-facing trigger         dog teeth configured for engagement with the one or more trigger         reaction dog pockets of the upper latch assembly;         such that when the one or more trigger dog teeth are disposed         within the one or more trigger reaction dog pockets, an upward         force applied to the land surface of the bumper element will         tend to cause relative axially-upward displacement of the bumper         so as to urge rotation of the lower latch assembly, wherein the         trigger element acts between the bumper element and through         engagement with the trigger dogs with the upper latch assembly         so as to force relative rotation between upper and lower latch         components to induce axial disengagement of the upper and lower         rotary latch components, whereupon continued application of the         upward force and resultant axial and rotary displacement of the         bumper element relative to the lower latch assembly will cause         withdrawal of the trigger dog teeth from the trigger dog         reaction pockets.

The rotary latch release mechanism may include a first axially-oriented biasing means acting between the upper and lower latch assemblies so as to bias the latch release mechanism toward the latched position, and a second axially-oriented biasing means acting between the movable bumper element and the trigger element so as to bias the bumper element axially downward relative to the trigger element.

The upper latch assembly may define a downward-facing upper ramp surface that is matingly engageable with an upward-facing lower ramp surface defined by the lower latch assembly, such that the application of an upward force to the land surface of the bumper element will bring the upper and lower ramp surfaces into sliding engagement so as to constrain the relative axial approach of the upper and lower latch assemblies while allowing relative rotation between the upper and lower latch assemblies.

In another aspect, the present disclosure teaches embodiments of a rotary latch release mechanism acting between (1) a generally cylindrical main body having a main body bore, and (2) a generally cylindrical load adaptor coaxially disposed within the main body bore and both axially and rotatably movable therein, with a lower end of the load adaptor being operatively engageable with an axial-load-actuated latching linkage disposed within the main body. In one embodiment, the latch release mechanism comprises:

-   -   a load adaptor extension coaxially mounted to an upper region of         the load adaptor and having a lower portion forming a skirt         defining a first annular space between the load adaptor         extension and an outer cylindrical surface of the load adaptor;     -   a primary trigger element having a primary trigger bore, in         which:         -   an upper portion of the primary trigger element is coaxially             disposed within said first annular space, and is mounted to             and carried by the skirt so as to be axially and             rotationally movable relative to the skirt within defined             constraints;         -   a lower portion of the primary trigger element extends over             an upper region of the main body and is axially movable             relative thereto; and         -   the primary trigger element carries a downward-facing             primary trigger reaction surface;     -   a secondary trigger element coaxially disposed within a         secondary annular space defined by the skirt and the primary         trigger element, wherein:         -   the secondary trigger element is mounted to and carried by             the skirt so as to be axially movable, within defined             constraints, relative to the skirt, but non-rotatable             relative to the skirt; and         -   the secondary trigger element is coupled to the primary             trigger element so as to be axially and rotationally movable             relative to the primary trigger element within defined             constraints;     -   a secondary trigger extension having a secondary trigger         extension bore and being coaxially mounted to a lower end of the         secondary trigger element;     -   a main body extension coaxially and fixedly mounted to an outer         cylindrical surface of the main body, said main body extension         having a cylindrical upper portion coaxially disposed within the         secondary trigger extension bore, wherein:         -   the inner and outer diameters of the cylindrical upper             portion of the main body extension substantially correspond             to the inner and outer diameters of the primary trigger             element;         -   the cylindrical upper portion of the main body extension             defines an upward-facing first reaction surface             (alternatively referred to herein as an “upward-facing dog             reaction surface”) configured for mating engagement with the             primary trigger reaction surface;         -   an external shoulder defining an upward-facing second             reaction surface is provided on a lower region of the main             body extension;         -   the main body extension is axially movable relative to, and             is co-rotatable with, the secondary trigger extension; and         -   the lower end of the secondary trigger extension is             configured to be engageable with the second reaction             surface.             In this embodiment, the primary and secondary trigger             elements are configured such that axial compressive load             applied to the load adaptor will be reacted by contact and             engagement of the first reaction surface with the primary             trigger reaction surface and the second reaction surface             with the secondary trigger extension, causing corresponding             axial displacement between the load adaptor and the main             body, thereby inducing rotation and axial movement of the             secondary trigger element relative to the primary trigger             element, thus generating torque and corresponding rotation             to unlatch the latching linkage.

Optionally, in alternative embodiments, a plurality of primary trigger dog teeth each comprising a primary trigger dog tooth load flank, a primary trigger dog tooth crest, and a primary trigger dog tooth lock flank, may be provided on the downward-facing reaction surface on the primary trigger element, with a corresponding plurality of mating reaction dog pockets, each defining a reaction pocket load flank, a reaction pocket crest, and a reaction pocket lock flank, being provided on the upward-facing dog reaction surface provided on the main body extension.

Several exemplary embodiments of latch release mechanisms in accordance with the present disclosure are described below, in the context of use with a CRT utilizing a J-latch to retain the grip surface of the CRT in its retracted position, and providing means for triggering the J-latch by application of set-down load without requiring the application of external rotation and latch actuation torque through the load adaptor.

EMBODIMENT #1 Rotary Cushion Bumper Reacted by Casing Friction (both CRTi and CRTe)

Embodiment #1 relies on tractional resistance to react latch actuation torque. In this embodiment, the latch release mechanism is carried by the lower latch assembly (comprising the grip assembly of a CRT), and has a movable land element (or cushion bumper) with a generally downward-facing land surface adapted for tractional engagement with the upper end of a tubular workpiece. Upward axial compressive movement of the movable land element relative to the lower rotary latch component, in response to contact with a tubular workpiece, causes the latch release mechanism to rotate the lower rotary latch component relative to the upper rotary latch component in the unlatching direction.

The latch release mechanism is further provided with biasing means (such as but not limited to a spring), for biasing the land surface to resist axial compressive displacement relative to the lower rotary latch component, correspondingly producing tractional resistance to rotary sliding between the land surface and the tubular workpiece. Thus arranged, with the upper and lower rotary latch components initially in the axially-latched position, and with the upper latch assembly (comprising the body assembly of a CRT) supported through the load adaptor to resist rotation relative to the tubular workpiece, axial compressive movement transmitted through the load adaptor to the upper rotary latch component relative to the tubular workpiece tends to urge rotation (as well as axial compressive stroke, if required) of the lower rotary latch component relative to the upper rotary latch component, and where tractional resistance between the land surface and the tubular workpiece is sufficient to exceed the latch actuation torque, the axial compressive movement causes rotation relative to the upper rotary latch component to move the lower rotary latch component to the unlatched position.

EMBODIMENT #2 Frictional Trigger Acting Between a Floating Load Adaptor and Main Body: CRTe with Stroke

Embodiment #2, like Embodiment #1, relies on tractional resistance to react latch actuation torque. In this embodiment, the upper latch assembly has a load adapter slidingly coupled to a main body to carry axial load while still allowing axial stroke. The upper rotary latch component is axially carried by the main body, but is rotationally coupled to the load adaptor. The lower latch assembly is carried by and is rotationally coupled to the main body, while allowing axial sliding, over at least some range of motion, when in the unlatched position. The lower latch assembly is further configured to carry a land surface for contact with a tubular workpiece to support set-down loads and to provide tractional resistance to rotation.

The latch release mechanism is carried by a selected one of the load adaptor and the main body, and has a generally axially-facing movable clutch surface adapted for tractional engagement with an opposing reaction clutch surface on the other of the load adaptor and the main body. Axial compressive stroking movement of the latch release mechanism after contact and engagement of the movable clutch surface with the reaction clutch surface, as urged by set-down force applied to the load adaptor, causes the latch release mechanism to urge rotation between the load adaptor and the main body in the unlatching direction. The latch release mechanism is further provided with biasing means (such as but not limited to a spring), for biasing the movable clutch surface to resist axial compressive displacement relative to the component on which it is carried (i.e., either the load adaptor or the main body), correspondingly producing tractional resistance to rotary sliding between the contacting movable clutch surface and the reaction clutch surface (or clutch interface).

Thus arranged, with the upper and lower rotary latch components initially in the axially-latched position, and with the load adaptor supported to generally allow free rotation relative to the main body and hence the tubular workpiece, axial compressive movement within the axial stroke allowance of the load adaptor relative to the main body tends to urge rotation (and axial compressive stroke, if required) of the upper rotary latch component relative to the lower rotary latch component. Where the tractional resistance of the clutch interface is sufficient to exceed the latch actuation torque (and perhaps some external resistance torque of the generally freely-rotating load adaptor), the axial compressive movement induces rotation of the upper rotary latch component relative to the lower rotary latch component to move to the unlatched position.

Where free rotation of the load adaptor is inhibited, the rotation urged by set-down load tends to urge sliding at the clutch interface and at the land-to-workpiece interface. The corresponding torque induced at these two interfaces, upon application of sufficient set-down load, will thus tend to induce sliding on one interface or the other. If sliding occurs on the land-to-workpiece interface, the rotation necessary to release the latch will occur. However, if sliding occurs at the clutch interface, then relative rotation of the latch components will not occur, rendering the latch release mechanism ineffective for its intended purpose in these particular circumstances. It may therefore be advantageous to provide means for increasing the torsional resistance of the clutch interface to increase the effective tractional resistance under application of axial load, such as by providing these mating surfaces as conically-configured surfaces to increase the normal force driving rotational tractional resistance, for a given axial load. Such modifications may be provided in the absence of or in combination with contouring or other surface treatments for increasing frictional resistance.

However, in all cases where it is desired to allow for re-latching, the tractional resistance to rotation occurring at the clutch interface will tend to impede the relative rotation of upper and lower rotary latch components if set-down load is required to effect re-latching. For certain applications it may be possible to reliably control the tractional response of these two interfaces by providing a selected combination of biasing spring force, contact surface geometry, and surface treatment of the clutch and land-to-workpiece surfaces, in coordination with load control sufficient to reliably prevent clutch interface slippage in support of latch release rotation for a first compressive load, while simultaneously allowing clutch interface slippage without resultant land-to-workpiece slippage to support re-latching, for a second selected compressive load in combination with applied rotation.

As described above, Embodiments #1 and #2 rely on the presence of sufficient tractional engagement between contacting components for reliable unlatching with set-down movement. In Embodiment #1, the only limiting tractional resistance is between the tubular workpiece and the cushion bumper, with the additional constraint that the latch actuation torque is further resisted by external support carrying the upper latch assembly. To state this otherwise, relative rotation between the upper rotary latch component and the tubular workpiece must be largely prevented (at least in the unlatching direction) to support grip engagement without externally-applied rotation.

In Embodiment #2, sufficient tractional resistance of the clutch interface is required, typically with the added constraint of free rotation of the load adaptor of the upper latch assembly. For applications where these boundary conditions can be readily and reliably met, Embodiments #1 and #2 can provide the benefits of faster cycle times and reduced risk of connection thread damage, plus the benefit of comparative mechanical simplicity. However, for applications where these boundary conditions cannot be readily achieved, means can be provided for releasing a J-latch independent of available tractional resistance or control of top drive rotation, as in alternative embodiments described below.

EMBODIMENT #3 Latch Release Mechanism Adapted for “Base Configuration”: CRTs Incorporating A Latching Tri-Cam Assembly

Embodiment #3 is configured to force relative rotation of the upper and lower rotary latch components through the latch release mechanism. In this embodiment:

-   -   the upper rotary latch component is rigidly carried by a main         body of the upper latch assembly;     -   the lower rotary latch component is rotationally and axially         constrained and carried by the lower latch assembly, which acts         in coordination with the main body to prevent relative rotary         and axial movement when the upper and lower rotary latch         components are latched;     -   the latch release mechanism acts between the upper and lower         latch assemblies and comprises four main elements, as follows:         -   a latching tri-cam assembly as disclosed in International             Publication No. WO 2010/006441 (Slack) and in U.S. Pat. No.             8,424,939 [the contents of which are incorporated herein in             their entirety, in jurisdictions where so permitted];         -   a trigger reaction ring having one or more downward-facing             reaction dog pockets rigidly attached to the upper latch             assembly;         -   a trigger element carried by the lower latch assembly and             having one or more upward-facing trigger dog teeth generally             mating and interacting with the downward-facing reaction dog             pockets; and         -   a movable land element also carried by the lower latch             assembly, and provided with a generally downward-facing land             surface adapted for axial compressive engagement with the             upper end of a tubular workpiece.

The movable land element and the trigger element are coupled to each other and to the lower latch assembly such that upward axial compressive movement or stroke of the movable land element relative to the lower latch assembly from a first (or land) position to a second (or fully-stroked) position, as urged by contact with a tubular workpiece, will urge rotation and downward axial movement of the trigger dog teeth. Initially, rotation of the trigger dog teeth is prevented by interaction with the reaction dog pockets which causes rotation of the lower rotary latch component relative to the upper rotary latch component to their unlatched position, and when the movable land element is fully stroked, the trigger dog teeth are fully retracted and disengaged from the reaction dog pockets. The retraction of the trigger dog teeth from the reaction dog pockets supports re-latching under application of external rotation in the re-latching direction. This embodiment preferably includes biasing means tending to resist both the axial compression of the movable land element and the retraction of the trigger element, so that the land and trigger elements return to their initial positions upon unloading and withdrawal from the tubular workpiece.

EMBODIMENT #4 Retracting Trigger Acting Between a Floating Load Adaptor and Main Body: CRTe with Stroke

Embodiment #4, like Embodiment #3, is configured to force relative rotation of the upper and lower rotary latch components through the latch release mechanism. In this embodiment:

-   -   the upper latch assembly includes a load adapter, coupled to a         main body so as to carry axial load while allowing axial stroke;     -   the upper rotary latch component is axially carried by the main         body but is rotationally coupled to the load adaptor;     -   the lower latch assembly (comprising the grip assembly of a CRT)         is carried by and rotationally coupled to the main body while         permitting axial movement, over at least some range of motion,         when the latch is in its unlatched position; and     -   the lower latch assembly is further configured to carry a land         surface for contact with a tubular workpiece:         -   to support set-down loads;         -   to enable relative rotation between the lower latch assembly             and the upper latch assembly by sliding at the contact with             the workpiece if the load adaptor resists rotation during             set-down due to restrictions imposed by the top drive; and         -   to enable moving from the unlatched to the latched position             by providing tractional resistance to rotation.

The latch release mechanism is configured to act between the sliding load adaptor and main body, and, similar to Embodiment #3, comprises three main elements:

-   -   reaction dog pockets carried by a selected one of the load         adaptor and the main body;     -   a primary trigger element having trigger dog teeth; and     -   a secondary trigger element carried by the other of the load         adaptor and the main body.

In the following discussion, it is assumed that the reaction dog pockets are upward-facing and are carried by the main body, and that the primary trigger element (having downward-facing trigger dog teeth) and the secondary trigger element (having a downward-facing standoff surface) are carried by the load adaptor. When the tool is in the latched position, the trigger dog teeth and the reaction dog pockets are configured for aligned engagement upon downward axial sliding movement of the load adaptor through its axial stroke, as urged by contact with a tubular workpiece.

An upward-facing reaction surface is also provided with the reaction dog pockets, and therefore is rigidly carried by the main body and arranged to contact the downward-facing standoff surface at an axial stroke position lower than required for engagement of the trigger dog teeth with the reaction dog pockets. The secondary trigger element and the primary trigger element are coupled to each other and to the load adaptor assembly such that downward axial compressive movement or stroke of the standoff surface relative to the load adaptor from a first (land) position to a second (fully-stroked) position, as urged by contact with a tubular workpiece, will urge both rotation and upward axial movement of the trigger dog teeth.

Initially, rotation of the trigger dog teeth is prevented by interaction with the reaction dog pockets, which causes rotation of the lower rotary latch component relative to the upper rotary latch component to their unlatched position, and when the secondary trigger element is fully stroked, the trigger dog teeth will be fully retracted and disengaged from the reaction dog pockets, and this retraction of the trigger dog teeth will support re-latching under application of external rotation in the re-latching direction. This embodiment preferably includes biasing means tending to resist both axial compression of the secondary trigger element and retraction of the primary trigger element, such that upon unloading and withdrawal from the tubular workpiece, the primary and secondary trigger elements return to their initial positions.

To further support reverse rotation under set-down load as needed to effect re-latching, the secondary trigger element may be provided as a secondary trigger assembly comprising a secondary trigger extension, having a downward-facing standoff surface, threaded to the secondary trigger element but rotationally keyed to the main body such that rotation in the direction of unlatching tends to move the standoff surface lower, causing compressive engagement of the standoff surface and the reaction surface at axially-higher positions, which prevents the premature engagement of the trigger dog teeth with the reaction dog pockets until the rotational position for re-latching has been reached.

EMBODIMENT #5 Internal Trigger CRTe

In Embodiment #5, a latch release mechanism has a longitudinal axis and acts between an upper latch assembly and a lower latch assembly, said upper and lower latch assemblies being coaxially aligned with the latch release mechanism, and wherein:

-   -   (a) the upper and lower latch assemblies are operable between:         -   a latched position, in which relative axial separation of             the upper and lower latch assemblies is constrained; and         -   an unlatched position, in which relative axial motion of the             upper and lower latch assemblies is permitted within a             defined range;     -    in response to application of relative rotation, and an         associated torque, between the upper and lower latch assemblies         in a first rotational direction;     -   (b) the upper latch assembly defines one or more trigger         reaction dog pockets; and     -   (c) the upper latch assembly axially carries a generally         cylindrical main body assembly having a main body bore;         wherein the latch release mechanism is coaxially disposed within         the main body bore and comprises:     -   (d) a bumper element coupled to the lower latch assembly, such         that when the bumper element is moved axially relative to the         lower latch assembly, the bumper element will also rotate         relative to the lower latch assembly; and     -   (e) a trigger element coupled to the bumper element and the         lower latch assembly so as to be at least axially movable         relative to the bumper element, and so as to be axially and         rotationally movable relative to the lower latch assembly within         a defined range, wherein the trigger element defines one or more         trigger dog teeth configured for axial engagement and         disengagement with the one or more trigger reaction dog pockets         of the upper latch assembly;         such that when the one or more trigger dog teeth are disposed         within the one or more trigger reaction dog pockets:     -   application of an axial force to the bumper element will tend to         cause axial stroking of the bumper element relative to the lower         latch assembly so as to urge relative rotation between the upper         and lower latch assemblies in the first rotational direction to         move the upper and lower latch assemblies from the latched         position to the unlatched position with the associated torque         transmitted through the trigger element; and     -   application of additional axial force and the resultant axial         and rotational displacement of the bumper element relative to         the lower latch assembly will cause withdrawal of the one or         more trigger dog teeth from the one or more trigger reaction dog         pockets.

In variant embodiments, the latch release mechanism may further comprise an over-running clutch (i.e., a clutch that transfers torque in one rotational direction but does not transfer torque in the opposite rotational direction) configured such that a torque applied to the bumper element in the first rotational direction will be transferred through the latch release mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described with reference to the accompanying Figures, in which numerical references denote like parts, and in which:

FIG. 1 illustrates a prior art internally-gripping casing running tool (CRTi) essentially corresponding to that shown in FIGS. 48 and 49 of U.S. Pat. No. 8,424,939.

FIGS. 2A and 2B, respectively, are isometric and sectional views of a prior art CRTi as in FIG. 1, fitted with an embodiment of a latch release mechanism in accordance with the present disclosure.

FIGS. 3A and 3B, respectively, are schematic elevation and isometric views of an exemplary embodiment of a latch release mechanism in accordance with the present disclosure, shown in the latched and unloaded position.

FIGS. 4A and 4B, respectively, are schematic elevation and isometric views of the latch release mechanism in FIGS. 3A and 3B, shown after application of axial load causing axial movement to initiate a latch release sequence.

FIGS. 5A and 5B, respectively, are schematic elevation and isometric views of the latch release mechanism in FIGS. 3A and 3B, shown after application of axial load to stroke the latch release mechanism so as to cause rotary movement sufficient to release the latch.

FIGS. 6A and 6B, respectively, are elevation and isometric views of the latch release mechanism in FIGS. 3A and 3B, shown after application of axial load to stroke the latch release mechanism so as to cause axial movement sufficient to withdraw the latch.

FIGS. 7A and 7B, respectively, are elevation and isometric views of the latch release mechanism in FIGS. 3A and 3B, shown after rotation to re-latch the latch, and after sufficient reduction of axial load to partially reset the latch release mechanism.

FIG. 8A is a cross-section through the tri-cam latching linkage and latch release mechanism of the modified CRTi tool in FIGS. 2A and 2B, shown in the latched and unloaded position.

FIG. 8B is a cross-section through the latch release mechanism of the modified CRTi tool in FIGS. 2A and 2B, shown in the latched and unloaded position.

FIG. 9A is a cross-section through the tri-cam latching linkage and latch release mechanism as in FIG. 8A, shown after application of axial load to stroke the latch release mechanism so as to cause rotary movement sufficient to release the latch.

FIG. 9B is a cross-section through the latch release mechanism in FIG. 8B, shown after the application of axial load so as to stroke the latch release mechanism to cause rotary movement sufficient to release the latch.

FIG. 10A is a cross-section through the tri-cam latching linkage and latch release mechanism in FIG. 8A, shown after the application of sufficient axial load to stroke the latch release mechanism so as to withdraw the trigger dog.

FIG. 10B is a cross-section through the latch release mechanism in FIG. 8B, shown after the application of sufficient axial load to stroke the latch release mechanism so as to withdraw the trigger dog.

FIG. 11A is a cross-section through the tri-cam latching linkage and latch release mechanism in FIG. 8A, shown after rotation to re-latch the latch release mechanism.

FIG. 11B is a cross-section through the latch release mechanism in FIG. 8A, shown after rotation to re-latch the latch release mechanism.

FIG. 12 illustrates a prior art CRTi fitted with an embodiment of a latch release mechanism in accordance with the present disclosure.

FIG. 13A is a cross-section through the tri-cam latching linkage and latch release mechanism of the modified CRTi in FIG. 12.

FIG. 13B is a cross-section through the latch release mechanism in FIG. 13A.

FIG. 14A is a cross-section through the tri-cam latching linkage and latch release mechanism of the modified CRTi in in FIGS. 13A and 13B, shown in the latched and unloaded position.

FIG. 14B is a cross-section through the latch release mechanism in FIG. 14A.

FIG. 15 is a cross-section through a prior art CRTe.

FIG. 16 is a cross-section through a prior art externally-gripping casing running tool (CRTe) fitted with an embodiment of a latch release mechanism in accordance with the present disclosure.

FIGS. 17A and 17B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIG. 16, shown in an initial latched position.

FIGS. 18A and 18B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 17A and 17B, shown after the application of sufficient set-down and corresponding displacement to cause axially downward movement of the floating load adaptor extension.

FIGS. 19A and 19B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 18A and 18B, shown after continued application of set-down load and corresponding displacement tending to unlatch the latching linkage.

FIGS. 20A and 20B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 19A and 19B, shown after further application of set-down load and corresponding displacement tending to disengage the trigger dog teeth from the reaction dog pockets so as to allow relative rotation between the main body assembly and the floating load adaptor.

FIGS. 21A and 21B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 20A and 20B, shown after the application of sufficient axial set-down load to unlatch the tri-cam latching linkage, with the floating load adaptor having moved upward to remove the set-down load.

FIGS. 22A and 22B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 21A and 21B, showing right-hand rotation of the floating load adaptor causing engagement of the standoff surface on the secondary trigger extension to move downward toward the reaction surface on the main body extension.

FIGS. 23A and 23B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 22A and 22B, showing right-hand rotation applied after set-down load and corresponding displacement to disengage the trigger dog teeth from the reaction dog pockets.

FIGS. 24A and 24B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 23A and 23B, showing set-down load reapplied to re-latch the latching linkage.

FIGS. 25A and 25B are cross-sections through the tri-cam latching linkage and latch release mechanism in FIGS. 24A and 24B, showing the latching linkage in the re-latched position.

FIG. 26 is a cross-section through an externally-gripping casing running tool (CRTe) internally configured with an embodiment of a latch release mechanism in accordance with the present disclosure and a variable-length axial linkage in accordance with International Application No. PCT/CA2021/000096.

FIG. 27 is a front elevation of the variable-length axial linkage and latch release mechanism of the CRTe in FIG. 26.

FIG. 28 is an isometric view of the variable-length axial linkage and latch release mechanism in FIG. 27, with the latch release mechanism shown in exploded view.

FIG. 29A is a cross-section through the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, and with the variable-length axial linkage in the latched position.

FIG. 29B is a front elevation of the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, with the drive cam body and cage extension sectioned, and with the variable-length axial linkage in the latched position.

FIG. 30A is a cross-section through the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, and with the latch release mechanism sufficiently stroked to move the variable-length axial linkage to an unlatched position.

FIG. 30B is a front elevation of the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, with the drive cam body and cage extension sectioned, and with the latch release mechanism sufficiently stroked to move the variable-length axial linkage to an unlatched position.

FIG. 31A is a cross-section through the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, and with the latch release mechanism fully stroked to retract the trigger dog teeth from the trigger reaction dog pockets.

FIG. 31B is a front elevation of the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, with the drive cam body and cage extension sectioned, and with the latch release mechanism fully stroked to retract the trigger dog teeth from the trigger reaction dog pockets.

FIG. 32A is a cross-section through the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, and with the lower latch assembly rotated relative to the upper latch assembly to relatch the variable-length axial linkage.

FIG. 32B is a front elevation of the variable-length axial linkage and latch release mechanism in FIG. 27, shown with the trigger spring hidden, with the lower portion of the drive cam body cut away to reveal the trigger dog teeth and trigger reaction dog pockets, with the drive cam body and cage extension sectioned, and with the lower latch assembly rotated relative to the upper latch assembly to relatch the variable-length axial linkage.

DETAILED DESCRIPTION

FIG. 1 illustrates a prior art internally-gripping CRT 100 essentially corresponding to the CRTi shown in FIGS. 48 and 49 of U.S. Pat. No. 8,424,939. CRT 100 includes a body assembly 110, a grip assembly 120, and a cage 500 linked to grip assembly 120. CRT 100 is shown in FIG. 1 as it would appear in the latched position and inserted into a tubular workpiece 101 (shown in partial cutaway). In this latched position, relative axial movement between body assembly 110 and grip assembly 120 is prevented, such that grip assembly 120 is held in its retracted position.

The upper end of body assembly 110 is provided with a load adaptor 111, illustrated by way of non-limiting example as having a conventional tapered-thread connection 112 for structural connection to a top drive quill (not shown) of a drilling rig (not shown). Grip assembly 120 includes a land surface 122 carried by a fixed bumper 121 rigidly attached to cage 500 of grip assembly 120. As described in U.S. Pat. No. 8,424,939 (but not shown herein), body assembly 110 carries an upper rotary latch component, and grip assembly 120 carries a lower rotary latch component, which is linked to cage 500 so as to be generally fixed against rotation and axial movement relative to cage 500 when in the latched position, but configured for rotary movement to an unlatched position in response to typically right-hand rotation of body assembly 110 relative to grip assembly 120, with the latch actuation torque corresponding to this rotary movement being reacted by tractional engagement of land surface 122 with tubular workpiece 101.

FIG. 2A illustrates a CRTi 130 generally corresponding to CRT 100 in FIG. 1, but modified to incorporate an embodiment of a rotary latch release mechanism (alternatively referred to herein as a trigger mechanism) in accordance with the present disclosure. CRTi 130 is shown in FIG. 2A as it appears in the latched position. In this particular embodiment, CRTi 130 includes a latch release mechanism 201 (schematically illustrated in figures that follow) comprising:

-   -   an upper rotary latch component provided in the form of a         trigger reaction ring 204 rigidly carried by body assembly 110,         and having one or more downward-facing trigger reaction dog         pockets 205, with each trigger reaction dog pocket 205 being         generally defined by a reaction pocket load flank 206, a         reaction pocket crest 207, and a reaction pocket lock flank 208;     -   a trigger element 210 having one or more upward-facing trigger         dog teeth 211, with each trigger dog tooth 211 being generally         defined by a trigger dog tooth load flank 212, a trigger dog         tooth crest 213, and a trigger dog tooth lock flank 214, wherein         each trigger dog tooth 211 engages a corresponding trigger         reaction dog pocket 205 when latch release mechanism 201 is in         the latched position as shown in FIG. 2A; and     -   a movable bumper 218 having a movable land surface 220, wherein         trigger element 210 and movable bumper 218 are carried by a         lower rotary latch component provided in the form of a cage         extension 222 rigidly coupled to cage 500.

Cage extension 222, trigger element 210, and movable bumper 218 are generally configured as a coaxially-nested group of closely-fitting cylindrical components, where relative rotary and translational movements between these components are constrained to keep them coaxially aligned, but also linked by cam pairs in the manner of cam followers and cam surfaces as described later herein.

FIGS. 3A and 3B, FIGS. 4A and 4B, FIGS. 5A and 5B, FIGS. 6A and 6B, and FIGS. 7A and 7B schematically illustrate the operative relationships of the various components of latch release mechanism 201, at sequential stages of the operation of latch release mechanism 201. Although latch release mechanism 201 is a three-dimensional rotary assembly, in order to facilitate a clear understanding of the structure and operation of latch release mechanism 201, the basic components of latch release mechanism 201 are shown in FIGS. 3A to 7B in a generally two-dimensional schematic manner, with the tangential (rotary) direction being transposed into the horizontal direction, and with the axial direction being transposed into the vertical direction.

FIGS. 3A and 3B illustrate latch release mechanism 201 in relation to a schematically-represented CRT, still in the fully-latched position, with a schematically-represented tubular workpiece 101 disposed slightly below movable bumper 218.

Reference number 301 represents an upper latch assembly rigidly coupled to body assembly 110 of the CRT, and having a trigger reaction dog pocket 205 and an upper rotary latch receiver 302. Reference number 310 represents a lower latch assembly comprising a cage extension 222 incorporating a lower rotary latch hook 312 shown in the latched position relative to upper rotary latch receiver 302. Upper latch assembly 301 carries an internal upper cam ramp surface 303, shown nearly in contact with an internal lower cam ramp surface 304 on cage extension 222, with an internal biasing spring 305 disposed and acting between body assembly 110 and cage extension 222. These features are shown to represent the internal reactions and forces operative between body assembly 110 and grip assembly 120 of the CRT, to facilitate an understanding the functioning of the CRT in coordination with latch release mechanism 201.

Cage extension 222 carries a movable bumper 218 having a movable land surface 220 and a trigger element 210. Movable bumper 218 is linked to trigger element 210 by a bumper-trigger cam follower 314 rigidly fixed to movable bumper 218 and movable within an axially-oriented bumper-trigger cam slot 315 (having an upper end 316 and a lower end 317) formed in trigger element 210, such that movable bumper 218 is axially movable relative to trigger element 210. A bumper-cage cam follower 318, rigidly fixed to cage extension 222, is constrained to move within a bumper-cage cam slot 319 formed in movable bumper 218 (with bumper-cage cam slot 319 having an upper end 320 and a lower end 321); and a trigger-cage cam follower 322, rigidly fixed to cage extension 222, is constrained to move within a trigger-cage cam pocket 324 provided in trigger element 210.

Notwithstanding the particular and exemplary arrangement of the components of the latch release mechanism 201 as described above and illustrated in FIGS. 3A and 3B, it will be apparent to persons skilled in the art that the choice of fixing the cam follower to one or the other of two components to be paired, and the cam profile in the other, is arbitrary with respect to the relative movement constraint, and corresponding freedom, associated with such a mechanism. Similarly, the choice of cam follower/cam surface as the means for providing the desired movement constraint is not intended to be in any way limiting. Persons skilled in the art will readily understand that generally equivalent mechanisms can be provided in other forms without departing from the intended scope of the present disclosure.

In the illustrated embodiment, bumper-trigger cam slot 315 is provided as an axially-oriented slot, closely fitting with the diameter of the associated bumper-trigger cam follower 314, and thus having a single degree of freedom to permit only relative axial sliding movement between trigger element 210 and movable bumper 218 but not relative rotation, with a trigger bias spring 326 being provided to act between trigger element 210 and movable bumper 218, in the direction of axial sliding, to bias movable bumper 218 downward relative to trigger element 210. Bumper-cage cam slot 319 is sloped at a selected angle relative to the vertical (shown by way of non-limiting example in FIGS. 3A and 3B as approximately 45 degrees) and is closely-fitting with the diameter of the associated bumper-cage cam follower 318 to provide a single degree of freedom linking relative axial movement of movable bumper 218 to rotation of cage extension 222. However, free movement of trigger-cage cam follower 322 is permitted within the trapezoidal trigger-cage cam pocket 324, constrained only by contact against cam constraint surfaces defining the perimeter of trigger-cage cam pocket 324, as follows:

-   -   a trigger advance cam surface 330, defining a horizontal lower         edge of trigger-cage cam pocket 324;     -   a trigger withdraw cam surface 332, defining a sloped right-side         edge of trigger-cage cam pocket 324, sloped at a selected angle         from the vertical;     -   a trigger re-latch cam surface 334, defining a horizontal upper         edge of trigger-cage cam pocket 324; and     -   a trigger reset cam surface 336, defining a vertical left-side         edge of trigger-cage cam pocket 324.

During typical operations, the operative status of latch release mechanism 201 may be characterized with reference to the position of trigger-cage cam follower 322 within trigger-cage pocket 324, as follows:

-   -   Start position: with trigger-cage cam follower 322 proximal to         the intersection of trigger reset cam surface 336 and trigger         advance cam surface 330 (as seen in FIGS. 3A, 3B, 4A, and 4B);     -   Advanced position: with trigger-cage cam follower 322 proximal         to the intersection of trigger advance cam surface 330 and         trigger withdraw cam surface 332 (as in seen FIGS. 5A and 5B);     -   Withdrawn position: with trigger-cage cam follower 322 proximal         to the intersection of trigger withdraw cam surface 332 and         trigger re-latch cam surface 334; and     -   Reset position: with trigger-cage cam follower 322 proximal to         the intersection of trigger re-latch cam surface 334 and trigger         reset cam surface 336.

When latch release mechanism 201 is in the latched position (as shown in FIGS. 3A and 3B), bumper-cage cam follower 318 is positioned toward upper end 320 of bumper-cage cam slot 319, and trigger-cage cam follower 322 is urged toward the start position within trigger-cage cam pocket 324 by trigger bias spring 326. At the same time, trigger bias spring 326 maintains the engagement of trigger dog tooth 211 within trigger reaction dog pocket 205, which engagement can position trigger dog tooth lock flank 214 in close opposition with reaction pocket lock flank 208 of trigger reaction dog pocket 205, as in this illustrated embodiment, so as to prevent accidental rotation of upper latch assembly 301 relative to lower latch assembly 310 as controlled by the selection of the mating flank angle and gap, where a more vertically-inclined angle is selected to more strongly resist rotation for a given trigger bias spring 326 force.

It will be apparent that upper rotary latch receiver 302 and lower rotary latch hook 312 (configured as a J-slot requiring axial displacement) already provides some protection against accidental rotation. However, for the type of J-latch typically employed in CRTs where axial displacement is not required and unlatching with only torque is allowed, the trigger dog tooth lock flank 214 and mating reaction pocket lock flank 208 provide the additional benefit of protection against accidental rotation.

In actual operation of the rotary latch release mechanism, the contact force reacted by tubular workpiece 101 against movable land surface 220 tends to build as CRTi 130 is lowered. However, as a matter of convenience for purposes of illustration in FIGS. 3A to 7B, upper latch assembly 301 will be considered as the datum, with tubular workpiece 101 being viewed as tending to move upward relative to upper latch assembly 301, and correspondingly tending to urge movable land surface 220 upward (rather than downward as in actual operation).

Referring now to FIGS. 4A and 4B, where the force of trigger bias spring 326 is sufficient to prevent relative movement between the components of latch release mechanism 201, force applied to movable land surface 220 will be transmitted through to cage extension 222, with upward movement being resisted until the force of internal biasing spring 305 is overcome, resulting in upward movement of the entire lower latch assembly 310, and correspondingly moving lower rotary latch hook 312 axially upward relative to upper rotary latch receiver 302. This upward movement is restricted by contact between internal upper cam ramp surface 303 and internal lower cam ramp surface 304, as illustrated in FIGS. 4A and 4B.

While such upward movement causing axial separation of lower rotary latch hook 312 from upper rotary latch receiver 302 is not a required movement for the type of J-latch typically employed for all CRTs, as will be known to persons skilled in the art, mating lower rotary latch hook 312 and upper rotary latch receiver 302 can alternatively be configured to disengage in response to applied torque only.

Independent of whether the applied load is first sufficient to overcome the force of the internal biasing spring 305, when sufficient force is applied by tubular workpiece 101 to overcome the force of trigger bias spring 326, movable bumper 218 will move upward, causing bumper-cage cam follower 318 to move downward within sloped bumper-cage cam slot 319, as shown in FIGS. 5A and 5B. The upward movement of movable bumper 218 tends to cause rotation of cage extension 222, but such rotation is resisted by the actuation torque acting between upper latch assembly 301 and lower latch assembly 310. This torque is transferred through movable bumper 218 to trigger element 210 via bumper-cage cam follower 318 and cam slot 319, and through trigger dog tooth load flank 212 to reaction pocket load flank 206 and thence back to upper latch assembly 301, thus internally reacting the latch actuation torque and causing trigger-cage cam follower 322 to move along trigger advance cam surface 330 to the advanced position within trigger-cage cam pocket 324, thus moving the rotary latch to its unlatched position as shown in FIGS. 5A and 5B. This movement is illustrated as right-hand rotation of upper latch assembly 301 relative to lower latch assembly 310.

As may be understood with reference to FIGS. 6A and 6B, further upward movement of movable bumper 218 continues to urge rotation of cage extension 222, causing: (1) movement of trigger-cage cam follower 322 to the withdrawn position within trigger-cage cam pocket 324, (2) resultant downward movement of trigger element 210, and (3) corresponding withdrawal of trigger dog tooth 211 from engagement with trigger reaction dog pocket 205. The slope angle of trigger withdraw cam surface 332 of trigger-cage cam pocket 324 is selected relative to the orientation of bumper-cage cam slot 319 to promote the withdrawal of trigger dog tooth 211 without jamming or otherwise inducing excess force considering the operative trigger bias spring 326 force and frictional forces otherwise tending to affect the withdrawal movement. Furthermore, it will be apparent that with trigger element 210 withdrawn from trigger reaction ring 204, upper latch assembly 301 is free to rotate relative to the lower latch assembly 310, and, more specifically, allows left-hand rotation of upper latch assembly 301 relative to lower latch assembly 310 to re-latch the tool.

This rotation supports movement of lower rotary latch hook 312 into engagement with upper rotary latch receiver 302 (i.e., the latched position), with corresponding actuation torque being resisted by tractional engagement of movable land surface 220 with tubular workpiece 101. In general, though, the portion of the set-down load carried by contact between internal upper cam ramp surface 303 and internal lower cam ramp surface 304, as a function of the associated cam ramp angle, tends to require less tractional engagement for this re-latching movement than required for unlatching in tools having different types of latch release mechanisms.

Referring now to FIGS. 7A and 7B, it will be seen that as the operational step to remove the tool from tubular workpiece 101 causes a reduction of the upward axial force acting on movable land surface 220, trigger bias spring 326 urges movable bumper 218 downward and correspondingly causes rotation of movable bumper 218 relative to cage extension 222, possibly with associated sliding at the interface between movable land surface 220 and tubular workpiece 101, and resultant tractional frictional force acting in the direction to maintain latching. This movement of movable bumper 218 and the force from trigger bias spring 326 tend to urge trigger element 210 to reverse the withdrawal movement just described, moving trigger dog tooth 211 upward. However, this upward movement is prevented when trigger dog tooth crest 213 slidingly engages reaction pocket crest 207, forcing trigger-cage cam follower 322 to move from the withdrawn position toward the reset position within trigger-cage cam pocket 324.

As movable bumper 218 continues to move downward, following the movement of tubular workpiece 101, a point is reached where trigger dog tooth crest 213 no longer engages (i.e., slides off) reaction pocket crest 207, thereby allowing trigger-cage cam follower 322 to move from the reset position and back toward the start position within trigger-cage cam pocket 324, thus returning latch release mechanism 201 to the operational state shown in FIGS. 3A and 3B, in which the tool is once again ready to initiate the operational sequence illustrated in FIGS. 3A and 3B through 7A and 7B.

CRTi Embodiment

FIG. 2B illustrates a CRTi 130 modified to incorporate an exemplary embodiment of a latch release mechanism 131 in accordance with the present disclosure, and a tri-cam latching linkage 132 generally as disclosed in U.S. Pat. No. 8,424,939. FIGS. 8A and 8B, FIGS. 9A and 9B, FIGS. 10A and 10B, and FIGS. 11A and 11B illustrate sequential operational stages of latch release mechanism 131.

In the embodiment illustrated in FIG. 2B, modified CRTi 130 comprises a body assembly 110 incorporating a load adaptor 111 for structural connection to the top drive quill of a drilling rig (not shown), a grip assembly 120 comprising a cage 500 and jaws 123, latch release mechanism 131, and tri-cam latching linkage 132. Tri-cam latching linkage 132 comprises an upper latch assembly 133 fixed to and carried by body assembly 110, and a lower latch assembly 134 fixed to and carried by grip assembly 120.

As illustrated in FIG. 8A, latch release mechanism 131 includes an upper latch assembly 133 comprising a drive cam body 400 carrying a plurality of drive cam latch hooks 401, and a drive cam housing 420, with drive cam body 400 being rigidly constrained to body assembly 110 of CRTi 130. Latch release mechanism 131 further includes a lower latch assembly 134 comprising a driven cam body 470, a driven cam housing 480, and a latch cam 490, with latch cam 490 having a plurality of latch cam latch hooks 491, and being rigidly constrained to grip assembly 120 of CRTi 130. Tri-cam latching mechanism 132 also includes an intermediate cam body 430 having load threads 431 on the inside surface that engage with load threads 402 on the outside surface of drive cam body 400.

A drive cam body-housing seal 403, a drive cam body-mandrel seal 404, a drive housing-driven housing seal 421, a drive cam body-cage seal 472, and a cage mandrel seal 501 define an annular piston area and a gas spring chamber 422. When pressurized with a gas, gas spring chamber 422 forms an internal gas spring that tends to urge the separation of upper latch assembly 133 and lower latch assembly 134, thereby tending to urge separation of body assembly 110 and grip assembly 120 to move latch release mechanism 131 between a first (unlatched) position and a second (latched) position. Such separation is resisted by matingly-engageable drive cam latch hooks 401 and latch cam latch hooks 491, which can be disengaged by the application of sufficient right-hand torque (i.e., latch actuation torque) and corresponding right-hand rotation of body assembly 110 relative to grip assembly 120. Tri-cam latching linkage 132 is considered to be in the latched position when drive cam latch hooks 401 and latch cam latch hooks 491 are engaged, and in the unlatched position when drive cam latch hooks 401 and latch cam latch hooks 491 are disengaged.

The following section details a mechanism that can be employed to use only axial compression and corresponding axial displacement to generate the right-hand torque and rotation required to unlatch the tri-cam latching linkage 132, having reference to FIG. 8B, which is a cross-section through latch release mechanism 131 shown in the latched position. For purposes of the discussion of this mechanism, the body assembly 110 will be considered as the datum, and the tubular workpiece 101 will be viewed as tending to move upward.

As illustrated in FIG. 8B, latch release mechanism 131 comprises a trigger reaction ring 410 fixed to body assembly 110, a trigger element 440, a trigger bias spring 449, a movable bumper 450 having a movable land surface 451, a bumper cam follower 452, and a cage extension 460 fixed to grip assembly 120. The components of latch release mechanism 131 and tri-cam latching linkage 132 are generally configured as a coaxially-nested group of closely-fitting cylindrical components, with relative rotary and translational movements between these components being constrained to first maintain them in coaxial alignment.

In operation, CRTi 130 with latch release mechanism 131 would first be inserted or “stabbed” into tubular workpiece 101 and lowered until movable land surface 451 contacts tubular workpiece 101, and the contact force resulting from tool weight and set-down load applied by the top drive (not shown) increases above the “trigger set-down load”, at which point latch release mechanism 131 has applied the required latch actuation torque and the displacement required to disengage drive cam latch hooks 401 and latch cam latch hooks 491. The gas spring will cause axial displacement of body assembly 110 relative to grip assembly 120, transitioning CRTi 130 with latch release mechanism 131 from the retracted position to the engaged position. This operational sequence differs from prior art CRT 100 in two ways:

-   -   First, CRTi 130 with latch release mechanism 131 does not         require externally-applied right-hand rotation to transition         between the retracted and engaged positions, which simplifies         the operational procedure.     -   Second, latch release mechanism 131 is designed such that it         does not rely on tractional engagement between movable land         surface 451 and tubular workpiece 101; instead, the latch         actuation torque is internally reacted, thus reducing         operational uncertainty.

As best understood with reference to FIG. 10B, trigger reaction ring 410 has one or more downward-facing trigger reaction dog pockets 411, each of which is generally defined by a reaction pocket load flank 412, a reaction pocket crest 413, and a reaction pocket lock flank 414, with each trigger reaction dog pocket 411 being engageable with a corresponding upward-facing trigger dog tooth 441. Each trigger dog tooth 441 is generally defined by a trigger dog tooth load flank 442, a trigger dog tooth crest 443, and a trigger dog tooth lock flank 444 (when the tool is in the latched position as shown in FIG. 8B). Movable bumper 450 and trigger element 440 are linked by bumper cam follower 452, fixed to movable bumper 450 and movable within a trigger cam slot 445 provided in trigger element 440, between an upper end 446 and a lower end 447 of trigger cam slot 445. Additionally, movable bumper 450 is linked to cage extension 460 by bumper cam follower 452, which is constrained to move within a bumper-cage cam slot 461 between an upper end 462 and a lower end 463 thereof. Trigger element 440 is linked to cage extension 460 by a trigger cam follower 448, which is fixed to trigger element 440 and is constrained to move within a cage cam pocket 464 provided in cage extension 460. Additionally, cage extension 460 is rigidly fixed to driven cam body 470.

It will be apparent to persons skilled in the art that the cam follower can be fixed to either of the two components to be paired, with the cam profile defined in the other of the two paired components, and that the design choice in this regard will typically be based on practical considerations such as efficiency of assembly, disassembly and maintenance. Similarly, the choice of cam follower/cam surface as the means for providing the desired movement constraint is not intended to be in any way limiting, where persons skilled in the art will understand that generally equivalent mechanisms can be provided in other forms.

In the embodiment shown in FIG. 8B, trigger cam slot 445 is provided as an axially-oriented slot, closely fitting with bumper cam follower 452, and thus generally providing a single degree of freedom to permit relative axial movement between trigger element 440 and movable bumper 450, but not permitting relative rotation. Trigger bias spring 449 is provided to act between trigger element 440 and movable bumper 450 in the direction of axial sliding, to bias movable bumper 450 downward. Bumper-cage cam slot 461 is sloped at a selected angle relative to the vertical (shown by way of non-limiting example in FIG. 8B as approximately 45 degrees), and is closely-fitting with the associated bumper cam follower 452 to provide a single degree of freedom linking relative axial movement of movable bumper 450 to rotation of cage extension 460. However, free movement of trigger cam follower 448 is permitted within trapezoidal cage cam pocket 464, constrained only by contact against cam surfaces defining the perimeter of cage cam pocket 464, as follows:

-   -   an advance cam surface 466, defining a flat upper edge of cage         cam pocket 464;     -   a withdraw cam surface 467, forming a helical path; and     -   a reset cam surface 469, defining an axially-oriented side edge         of cage cam pocket 464.

During typical operations, the operative status of latch release mechanism 131 may be characterized with reference to the position of trigger cam follower 448 within cage cam pocket 464, as follows:

-   -   Start position: with trigger cam follower 448 proximal to the         intersection of reset cam surface 469 and advance cam surface         466;     -   Advanced position: with trigger cam follower 448 proximal to the         intersection of advance cam surface 466 and withdraw cam surface         467;     -   Withdrawn position: with trigger cam follower 448 proximal to         withdraw cam surface 467; and     -   Reset position: with trigger cam follower 448 proximal to reset         cam surface 469.

With the latch release mechanism in the latched position as in FIG. 8B, with bumper cam follower 452 positioned at lower end 463 of bumper-cage cam slot 461, trigger bias spring 449 will urge trigger cam follower 448 toward the start position within cage cam pocket 464, while simultaneously maintaining the engagement of trigger dog teeth 441 within corresponding trigger reaction dog pockets 411. This engagement of trigger dog teeth 441 disposes trigger dog tooth lock flanks 444 in close opposition to corresponding reaction pocket lock flanks 414 so as to prevent accidental rotation of upper latch assembly 133 relative to lower latch assembly 134 as controlled by the selection of the mating flank angle and gap. If necessary, a more axially-aligned camming surface may be selected to more strongly resist rotation for a given force exerted by trigger bias spring 449.

Referring now to FIG. 9B, when sufficient force is applied by tubular workpiece 101 to overcome the force of trigger bias spring 449, movable bumper 450 moves upward, causing bumper cam follower 452 to move axially upward within bumper-cage cam slot 461. This axially-upward axial movement tends to rotate cage extension 460, but such rotation is resisted by the latch actuation torque acting between upper latch assembly 133 and lower latch assembly 134, which torque is transmitted through movable bumper 450 to trigger element 440 via bumper cam follower 452 and trigger cam slot 445, and through trigger dog tooth load flank 442 to reaction pocket load flank 412 and to upper latch assembly 133. This causes the latch actuation torque to be internally reacted, and causes trigger cam follower 448 to move along advance cam surface 466 to the advanced position within cage cam pocket 464, thereby disengaging drive cam latch hooks 401 from latch cam latch hooks 491 and changing the state of tri-cam latching linkage 132 from the latched position as in FIG. 8A to the unlatched position as in FIG. 9A, through right-hand rotation of upper latch assembly 133 relative to lower latch assembly 134.

Once drive cam latch hooks 401 and latch cam latch hooks 491 have disengaged, the gas spring urges separation of upper latch assembly 133 from lower latch assembly 134. It is at this point in the operational sequence of casing running that a combination of axial tension and rotation will be applied during the course of connection make-up to induce right-hand rotation of upper latch assembly 133 relative to lower latch assembly 134. During this stage of operation, latch release mechanism 131 will not interfere with the regular function of the casing running tool.

Further upward movement of movable bumper 450 continues to urge rotation of cage extension 460 and, therefore, movement of trigger cam follower 448 to the withdrawn position within cage cam pocket 464, thereby moving trigger element 440 down and correspondingly withdrawing trigger dog teeth 441 from engagement with trigger reaction dog pockets 411 as shown in FIG. 10B. The angle of withdraw cam surface 467 relative to sloped bumper-cage cam slot 461 may be selected so as to promote the withdrawal of trigger dog teeth 441 from engagement with trigger reaction dog pockets 411 without jamming or otherwise inducing force in excess of the operative trigger bias force and frictional forces otherwise tending to affect the withdrawal movement.

With trigger element 440 withdrawn from trigger reaction ring 410 as shown in FIG. 10B, trigger dog tooth lock flank 444 is no longer opposite reaction pocket load flank 412, so upper latch assembly 133 can be rotated relative to lower latch assembly 134 in order to re-latch tri-cam latching linkage 132. As may be seen in FIG. 11A, this rotation of upper latch assembly 133 relative to lower latch assembly 134 causes latch cam latch hooks 491 to move into engagement with drive cam latch hooks 401 (i.e., the latched position), with the corresponding actuation torque induced by this rotation being resisted by tractional engagement of movable land surface 451 with tubular workpiece 101.

Referring now to FIG. 11B, with CRTi 130 thus in the re-latched position, as the operational step of removing CRTi 130 from tubular workpiece 101 reduces the axial force acting on movable land surface 451, trigger bias spring 449 urges movable bumper 450 downward and correspondingly causes movable bumper 450 to rotate relative to cage extension 460, with possible attendant sliding between movable land surface 451 and tubular workpiece 101. Tractional frictional force from trigger bias spring 449 thus tends to urge trigger element 440 to reverse the withdrawal movement described above, moving trigger dog teeth 441 upward. However, this upward movement of trigger dog teeth 441 is prevented by sliding engagement of trigger dog tooth crests 443 with reaction pocket crest 413, forcing trigger cam follower 448 to move from the withdrawn position to the reset position within cage cam pocket 464. As movable bumper 450 continues to move downward, following the movement of tubular workpiece 101, a point is reached where trigger dog tooth crests 443 no longer engage (i.e., they slide off) reaction pocket crest 413, thereby allowing trigger cam follower 448 to move from the reset position to the start position within cage cam pocket 464, thus returning latch release mechanism 131 to the position shown in FIG. 8A, from which position the operational sequence shown in FIGS. 8A to 11B can be repeated.

Frictional/Inertial CRTi Embodiment

There will now be described a latch release mechanism which in quasi-static operation relies on tractional resistance between movable land surface 451 of movable bumper 450 and tubular workpiece 101. This latch release mechanism is a modification to the latch release mechanism 131 described previously herein under the heading “CRTi Embodiment”. As used in this disclosure, the phrase “quasi-static operation” with respect to a latch release mechanism is to be understood as referring to operation of the mechanism such that axial load is applied in a sufficiently slow manner that dynamic effects associated therewith are minimal or negligible.

FIG. 12 is a sectional view of a prior art CRTi 135 fitted with a tri-cam latching linkage 132 and a latch release mechanism 136 carried by lower latch assembly 134 and comprising a movable bumper 450, a bumper cam follower 452 fixed to movable bumper 450, a trigger bias spring 520, and a cage extension 510, which are generally configured as a coaxially-nested group of closely-fitting cylindrical components, with relative rotary and translational movements between these components being constrained so as to keep them coaxially aligned. Tri-cam latching linkage 132, movable bumper 450, and bumper cam follower 452 in FIG. 12 are identical to those previously described under the “CRTi Embodiment” heading and depicted in FIGS. 8A and 8B.

As best understood with reference to FIGS. 13A and 13B, movable bumper 450 and cage extension 510 are linked by bumper cam follower 452, which is movable within a cage cam slot 511 provided in cage extension 510 and between an upper end 512 and a lower end 513 of cage cam slot 511. Cage cam slot 511 is sloped at a selected angle (shown by way of non-limiting example in FIG. 13B as approximately 45 degrees) relative to the longitudinal axis of the tool, and is closely-fitting with the associated bumper cam follower 452, which defines a translational-rotational relationship between movable bumper 450 and cage extension 510. Additionally, cage extension 510 is rigidly fixed to driven cam body 470, and trigger bias spring 520 is provided to act between cage extension 510 and movable bumper 450 to bias movable bumper 450 axially downward, as well as biasing bumper cam follower 452 to be in contact with lower end 513 of cage cam slot 511.

It will be apparent to persons skilled in the art that bumper cam follower 452 can be fixed to either one of the two components to be paired, with the cam profile being defined in the other one of the paired components. The design choice in this regard will typically be based on practical considerations including efficiency of assembly, disassembly, and maintenance. Similarly, the choice of cam follower/cam surface as the means for providing the desired movement constraint is not intended to be in any way limiting; persons skilled in the art will understand that functionally effective alternative mechanisms can be provided in other forms.

For purposes of the present discussion, body assembly 110 will be considered as the datum, relative to which tubular workpiece 101 will be viewed as tending to move upward. As shown in FIGS. 13A and 13B, when tri-cam latching linkage 132 is in the latched position, bumper cam follower 452 will be positioned at lower end 513 of cage cam slot 511 due to the axial downward force applied by trigger bias spring 520. In operation, CRTi 135 with latch release mechanism 136 will be lowered until movable land surface 451 on movable bumper 450 contacts tubular workpiece 101, and the contact force resulting from tool weight and set-down load applied by the top drive (not shown) increases above the “trigger set-down load”, at which point latch release tubular workpiece 136 will have applied the required latch actuation torque and the rotation required to disengage drive cam latch hooks 401 from latch cam latch hooks 491.

As illustrated in FIGS. 14A and 14B, when sufficient force is applied in a quasi-static manner by tubular workpiece 101 to overcome the force of trigger bias spring 520, movable bumper 450 will move upward, generating torque between itself and cage extension 510 due to the interaction of bumper cam follower 452 within cage cam slot 511, which torque, for the movable bumper 450, must be reacted by tractional engagement of movable land surface 451 with tubular workpiece 101, which tractional engagement, if sufficient, will result in rotation of cage extension 510.

The rotation of cage extension 510 will be resisted by the latch actuation torque acting between upper latch assembly 133 and lower latch assembly 134. The latch actuation torque will be transmitted from upper latch assembly 133 to load adaptor 111, and in turn must be reacted by the top drive, thereby disengaging drive cam latch hooks 401 from latch cam latch hooks 491, and resulting in movement of tri-cam latching linkage 132 from a latched position as shown in FIG. 13A to an unlatched position as shown in FIG. 14A, through right-hand rotation of upper latch assembly 133 relative to lower latch assembly 134. Once drive cam latch hooks 401 and latch cam latch hooks 491 have disengaged, a gas spring associated with latch release mechanism 136 (generally as previously described with reference to latch release mechanism 131) will urge upper latch assembly 133 to separate from lower latch assembly 134.

It will be apparent to persons skilled in the art that the described latch release mechanism 136 will be able to generate the latch actuation torque and corresponding rotation required to move CRTi 135 from a disengaged position to an engaged position by means of quasi-static application of axial set-down load and displacement only, provided that the following two boundary conditions can be readily met:

-   -   1. The tractional engagement between movable land surface 451         and tubular workpiece 101 is sufficient to react latch actuation         torque; and     -   2. The top drive has sufficient torque resistance to react latch         actuation torque.

In instances where the above two conditions can be readily and reliably met, latch release mechanism 136 can provide the benefits of faster cycle times, operational simplicity, and comparative mechanical simplicity.

Additionally, the nature of the tool's operation can be taken advantage of to supplement the tractional engagement between movable land surface 451 and tubular workpiece 101, i.e., movable bumper 450 can be designed with a high moment of inertia about the tool's axis relative to the combined moment of inertia of the cage extension 510 and grip assembly 120, and when the set-down load is applied with sufficient speed, the cage extension 510 and grip assembly 120 will have a greater tendency to rotationally accelerate, causing right-hand rotation of upper latch assembly 133 relative to lower latch assembly 134, and disengaging drive cam latch hooks 401 from latch cam latch hooks 491.

To disengage CRTi 135 from tubular workpiece 101, set-down load and left-hand torque are applied to load adaptor 111 and are reacted between movable bumper 450 and tubular workpiece 101. When the set-down load and left-hand torque are sufficient, upper latch assembly 133 will rotate in the left-hand direction relative to lower latch assembly 134, causing drive cam latch hooks 401 to move into engagement with latch cam latch hooks 491 (i.e., into the latched position), with the corresponding torque induced by this rotation being resisted by tractional engagement of movable land surface 451 with tubular workpiece 101.

The operational step of removing CRTi 135 from tubular workpiece 101 will reduce the axial force acting on movable land surface 451, with trigger bias spring 520 urging movable bumper 450 downward and correspondingly causing movable bumper 450 to rotate relative to cage extension 510, with possible attendant sliding between movable land surface 451 and tubular workpiece 101 and resultant tractional frictional force acting in the direction to maintain latching. With sufficient axial downward movement of tubular workpiece 101, bumper cam follower 452 will contact lower end 513 of cage cam slot 511, thus returning latch release mechanism 136 to the position shown in FIG. 13A, from which position the operational sequence shown in FIGS. 13A through 14B can be repeated.

CRTe Embodiment

FIG. 15 is a sectional view of a prior art externally-gripping casing running tool (CRTe) 140 comprising a main body assembly 150, which has a main body upper housing 151 rigidly fixed to a main body lower housing 152, a floating load adaptor 160 for structural connection to the top drive quill of a drilling rig (not shown), a grip assembly 170 that rigidly carries a bumper 171, and a tri-cam latching linkage 180 comprising an upper latch assembly 181 axially fixed to main body assembly 150, and a lower latch assembly 183 fixed to and carried by grip assembly 170. Upper latch assembly 181 is rotationally coupled to floating load adaptor 160, and comprises a drive cam 184 that carries a plurality of drive cam latch hooks 185, plus a drive cam housing 186. Lower latch assembly 183 comprises a driven cam 187, plus a latch cam 188 that carries a plurality of latch cam latch hooks 189.

As shown in FIG. 15, an upper cam-housing seal 190, a main body-housing upper seal 191, a lower cam-housing seal 192, a main body-housing lower seal 193, a lower cam-cage seal 194, and a upper cam-cage seal 195 define a gas spring chamber 196, with lower cam-housing seal 192 and upper cam-cage seal 195 defining a piston area carried by lower latch assembly 183. When pressurized with a gas, gas spring chamber 196 forms an internal gas spring that tends to urge separation of upper latch assembly 181 from lower latch assembly 183, and thereby tending to urge separation of main body upper housing 151 from grip assembly 170 so as to move CRTe 140 from a retracted position to an engaged position relative to tubular workpiece 101.

Such separation is resisted by matingly-engageable drive cam latch hooks 185 and latch cam latch hooks 189, which can be disengaged by the application of sufficient right-hand torque (i.e., latch actuation torque) and corresponding right-hand rotation of floating load adaptor 160 relative to main body assembly 150. In the prior art CRTe 140, latch actuation torque is applied through floating load adaptor 160, and is reacted through tractional engagement between tubular workpiece 101 and a land surface 172 provided on bumper 171. The tri-cam latching linkage 180 is considered to be in the latched position when drive cam latch hooks 185 and latch cam latch hooks 189 are engaged, and in the unlatched position when drive cam latch hooks 185 and latch cam latch hooks 189 are disengaged.

As also shown in FIG. 15, floating load adaptor 160 has a floating load adaptor upper axial shoulder 161 that permits the transfer of axial tension loads through contact with an axial shoulder 154 of the main body assembly 150. Additionally, floating load adaptor 160 has a floating load adaptor lower axial shoulder 162 that permits the transfer of axial compression loads through contact with an axial shoulder 182 on upper latch assembly 181 which in turn transfers the axial compression loads to main body upper housing 151. The axial distance between axial shoulder 154 on main body upper housing 151 and axial shoulder 182 on upper latch assembly 181 is greater than the axial distance between upper axial shoulder 161 and lower axial shoulder 162 on floating load adaptor 160, thereby providing an axial range through which floating load adaptor 160 can move without transferring axial tension or compressive loads to main body assembly 150.

FIG. 16 illustrates a CRTe 197 substantially corresponding to prior art CRTe 140 of FIG. 15 but fitted with a latch release mechanism 198 that can be employed to use only axial compression and corresponding axial displacement to generate the right-hand torque (i.e. latch actuation torque) and rotation required to unlatch the tri-cam latching linkage 180, allowing CRTe 197 to transition from the retracted position to the engaged position and then return to the retracted position to facilitate repetition of the casing make-up and hoisting process involved in constructing an oil and gas well.

FIG. 16 shows CRTe 197 in the latched position. Latch release mechanism 198 comprises:

-   -   a load adaptor extension 163, fixed to floating load adaptor 160         and comprising a downward-extending skirt 165;     -   a primary trigger element 600 (alternatively referred to as         primary trigger 600) coaxially disposed within load adaptor         extension 163; a trigger bias spring 618;     -   a secondary trigger element 620 (alternatively referred to as         secondary trigger 620);     -   a secondary trigger extension 630;     -   a main body extension 640;     -   a clamp ring 650; and     -   a main body lock 660.         These components of latch release mechanism 198 are generally         configured as a coaxially-nested group of closely-fitting,         generally cylindrical components, with relative rotational and         translational movements between these components being         constrained to keep them in coaxial alignment as will be         described in greater detail below.

In operation, CRTe 197 would first be inserted or “stabbed” over tubular workpiece 101, and the contact force resulting from tool weight and set-down load applied by the top drive (not shown) would increase, causing corresponding axial displacement between main body assembly 150 and floating load adaptor 160, enabling latch release mechanism 198 to generate the required latch actuation torque and corresponding rotation to unlatch tri-cam latching linkage 180, with the gas spring causing axial displacement between grip assembly 170 and main body assembly 150 transitioning CRTe 197 from the an initial retracted position to an engaged position. This operational sequence for CRTe 197 differs from the operation of prior art CRTe 140 in two ways:

-   -   First, CRTe 197 does not require externally-applied right-hand         rotation to transition between the retracted and engaged         positions, thus simplifying the operational procedure.     -   Second, latch release mechanism 198 of CRTe 197 is configured         such that it does not rely on tractional engagement between land         surface 172 and tubular workpiece 101; instead, the latch         actuation torque is internally reacted, thus reducing         operational uncertainty.

The following discussion describes how latch release mechanism 198 generates latch actuation torque and corresponding rotation by means of set-down load and axial displacement only.

FIG. 17A is a cross-section through CRTe 197, with the grip assembly 170, tubular workpiece 101, and main body lower housing 152 hidden for clarity, and FIG. 17B is a section through latch release mechanism 198 of CRTe 197, shown in both views in an initial latched position. Load adaptor extension 163 is rigidly fixed to floating load adaptor 160 by one or more load adaptor lugs 164, and rigidly carries one or more load adaptor cam followers 601, each of which is constrained to move within a primary trigger cam slot 606 provided by primary trigger 600 and within a secondary trigger cam slot 621 provided by secondary trigger 620. Primary trigger cam slot 606 also has a vertical lower portion 608 contiguous with upper portion 607. Upper portion 607 of primary trigger cam slot 606 is sloped at a selected angle from the vertical (which angle may vary along the length of upper portion 607). The relative axial and rotational movements between load adaptor extension 163 and primary trigger 600 are therefore bounded by upper and lower portions 607 and 608 of primary trigger cam slot 606.

Secondary trigger cam slot 621 is axially oriented and closely fitting to load adaptor cam follower 601, thereby coupling the rotation of load adaptor extension 163 and secondary trigger 620. Secondary trigger cam slot 621 has a lower end 623, plus an upper end 622 which load adaptor cam follower 601 is biased to be in contact with by trigger bias spring 618, which acts between secondary trigger 620 and load adaptor extension 163 to apply an axially-downward biasing force to secondary trigger 620. Relative axial movement between load adaptor extension 163 and secondary trigger 620 is therefore constrained within the upper end 622 of secondary trigger cam slot 621 and secondary trigger cam slot lower end 623.

Secondary trigger 620 rigidly carries one or more secondary trigger cam followers 624, each of which is close-fitting within a dog retraction cam slot 612 provided on primary trigger 600. Each dog retraction cam slot 612 has an upper end 613, which is circumferentially oriented and constrains secondary trigger 620 and primary trigger 600 to initially be axially coupled, and which transitions to a lower end 614 that is sloped at a selected angle (which angle may vary along the length of lower end 614) from the vertical, and is close-fitting to a corresponding secondary trigger cam follower 624 to define a translational-rotational relationship between secondary trigger 620 and primary trigger 600. Relative axial and rotational movement between secondary trigger 620 and primary trigger 600 is therefore constrained within upper and lower ends 613 and 614 of dog retraction cam slots 612.

Referring still to FIGS. 17A and 17B, secondary trigger extension 630 has a secondary trigger extension thread 632, with a defining helix in the left-hand direction, that engages a secondary trigger thread 625 provided on secondary trigger 620. Additionally, secondary trigger extension 630 has a secondary trigger extension lug 633 closely fitting to axially-oriented slots 647 provided on main body extension 640 so as to couple the rotation of main body extension 640 and secondary trigger extension 630. Main body lock 660 is held fixed to main body upper housing 151 by main body lock lugs 661. Clamp ring 650 is axially bolted to main body lock 660, with the axial load generated from the bolted connection being transferred into a clamp ring load shoulder 651 provided on clamp ring 650, to a main body extension load shoulder 648 provided on main body extension 640, and in turn reacted between a main body extension lock surface 649 and an upper housing lock surface 153 provided on main body assembly 150, which engagement allows main body extension 640 to tractionally resist torsional loads that may be generated by latch release mechanism 198. Thus arranged, main body extension 640 can first be assembled onto main body assembly 150 and rotationally positioned, and then clamp ring 650 can be secured, effectively rigidly connecting main body extension 640 to main body assembly 150.

As shown in FIG. 17B, a plurality of primary trigger dog teeth 602, each comprising a primary trigger dog tooth load flank 603, a primary trigger dog tooth crest 604, and a primary trigger dog tooth lock flank 605, may be provided on a downward-facing primary trigger reaction surface 615 on primary trigger 600, with a corresponding plurality of mating reaction dog pockets 642, each defining a reaction pocket load flank 643, a reaction pocket crest 644, and a reaction pocket lock flank 645 being provided on an upward-facing dog reaction surface 646 provided on main body extension 640. In this illustrated embodiment, primary trigger dog teeth 602 initially are rotationally aligned with but axially separated from corresponding mating reaction dog pockets 642.

FIG. 18A is a sectional view of CRTe 197, and FIG. 18B is a sectional view of latch release mechanism 198, both shown after contact between tubular workpiece 101 and bumper 171 has been established and sufficient axial set-down load and corresponding displacement have been generated to cause load adaptor extension 163, floating load adaptor lug 164, primary trigger 600, load adaptor cam follower 601, secondary trigger 620, secondary trigger cam follower 624 and secondary trigger extension 630 to translate axially downwards until primary trigger dog tooth crests 604 and their corresponding reaction pocket crests 644 initiate contact, at which point a standoff surface 631 provided on secondary trigger extension 630 is close to but not in contact with a second reaction surface 641 provided on main body extension 640.

Referring to FIGS. 19A and 19B, continued set-down load and corresponding displacement will cause primary trigger 600 to begin to move axially upwards, and to rotate in the right-hand direction, tending to unlatch tri-cam latching linkage 180, as a result of the constraints imposed on primary trigger 600 by the engagement of load adaptor cam follower 601 in the upper portion 607 of primary trigger cam slot 606. This rotation causes the engagement of primary trigger dog tooth load flank 603 with reaction pocket load flank 643, producing torque on main body extension 640 in the direction tending to unlatch tri-cam latching linkage 180. The torque applied to main body extension 640 is resisted by tractional engagement between main body extension lock surface 649 and upper housing lock surface 153 and is transferred into main body assembly 150. It will now be apparent that the latch release mechanism 198 is able to generate the torque and corresponding rotation in the direction tending to unlatch the tri-cam latching linkage 180 with the application of set-down load and displacement only.

Referring now to FIGS. 20A and 20B, further set-down load and corresponding axial displacement will cause secondary trigger cam followers 624 to engage lower ends 614 of dog retraction cam slots 612. This engagement tends to move primary trigger dog teeth 602 axially upward relative to main body extension 640, transferring the axial set-down load initially reacted between primary trigger dog tooth crests 604 and reaction pocket crests 644 to be reacted between standoff surface 631 and second reaction surface 641. With sufficient set-down load and corresponding displacement, primary trigger dog teeth 602 will become completely disengaged from reaction dog pockets 642, allowing relative rotation between the main body assembly 150 and floating load adaptor 160 in either direction.

FIGS. 21A and 21B, respectively, are sectional views of CRTe 197 and latch release mechanism 198, both shown after sufficient set-down load has been applied to unlatch tri-cam latching linkage 180 whereupon floating load adaptor 160 has been moved axially upwards, removing the axial set-down load. At this point, right-hand (or left-hand) rotation can be applied to floating load adaptor 160 to make up (or break out) the casing string connection. As shown in FIGS. 22A and 22B, the application of right-hand rotation between floating load adaptor 160 and main body assembly 150 will cause standoff surface 631 to move axially downwards due to the left-hand thread formed by secondary trigger extension thread 632 and secondary trigger thread 625, which downward axial movement in turn causes standoff surface 631 to engage second reaction surface 641 at relatively higher axial positions of floating load adaptor 160.

Alternatively, as shown in FIGS. 23A and 23B, right-hand rotation can be applied immediately after the axial set-down load and corresponding displacement are sufficient to disengage primary trigger dog teeth 602 from the corresponding reaction dog pockets 642, rather than moving floating load adaptor 160 axially upwards and then applying right-hand rotation. In this scenario, standoff surface 631 engages second reaction surface 641, and the application of right-hand rotation to floating load adaptor 160 will generate axially-upward force and corresponding displacement of secondary trigger 620. The axially-upward displacement of secondary trigger 620 causes load adaptor cam follower 601 to engage lower portion 608 of primary trigger cam slot 606.

In either case, right-hand rotation will cause standoff surface 631 to move axially downward, and when set-down load is reapplied to re-latch tri-cam latching linkage 180, standoff surface 631 will engage second reaction surface 641, thereby preventing primary trigger dog teeth 602 from re-engaging reaction dog pockets 642, and thus supporting the application of torque and rotation in the left-hand direction tending to re-latch tri-cam latching linkage 180, as depicted in FIGS. 24A and 24B. With tri-cam latching linkage 180 in the latched position, grip assembly 170 will now be retracted from tubular workpiece 101, while bumper 171 is still in contact with tubular workpiece 101.

FIGS. 25A and 25B show CRTe 197 in the re-latched position. As the operational step of removing CRTe 197 from tubular workpiece 101 reduces the axial force acting on land surface 172, trigger bias spring 618 urges secondary trigger 620 downward, and correspondingly causes primary trigger 600 to rotate in the left-hand direction and to move axially downwards relative to floating load adaptor 160. However, downward movement of primary trigger 600 is impeded by sliding engagement of primary trigger dog tooth crests 604 and dog reaction surfaces 646. As floating load adaptor 160 continues to move upward, a point is reached where primary trigger dog tooth crests 604 no longer engage (i.e., they slide off) dog reaction surfaces 646, thus allowing primary trigger dog teeth 602 to re-engage reaction dog pockets 642. Further axially-upward movement of floating load adaptor 160 will leave primary trigger dog teeth 602 rotationally aligned but axially separated from reaction dog pockets 642, thus returning latch release mechanism 198 to the position shown in FIGS. 17A and 17B, from which position the operational sequence illustrated in FIGS. 17A through 25B can be repeated.

Having reference to the preceding description of the operation of latch release mechanism 198, it will be apparent to persons skilled in the art that:

-   -   the shape of primary trigger cam slot 606 determines the         relationship between relative rotational and axial motions         between load adaptor extension 163 and primary trigger 600; and     -   the angle from vertical of primary trigger cam slot 606 may be         selected to vary along its length to coordinate the relative         rotational and axial motions, and to control contact stresses         and internal stresses generated as latch release mechanism 198         is actuated.

It will also be apparent to persons skilled in the art that:

-   -   primary trigger cam slot 606 of CRTe 197 is functionally         equivalent to bumper-cage cam slot 319 of the exemplary         embodiment shown in FIGS. 3A to 7B, bumper-cage cam slot 461 of         CRTi 130 shown in FIGS. 8B, 9B, 10B, and 11B, and cage cam slot         511 of CRTi 135 shown in FIGS. 13B and 14B; and     -   as with primary trigger cam slot 606, the angle from vertical of         bumper-cage cam slot 319, bumper-cage cam slot 461, and cage cam         slot 511 may be selected to vary along their respective lengths         to coordinate the relative rotational and axial motions, and to         control contact stresses and internal stresses generated as the         respective latch release mechanisms are actuated.

Internal Trigger CRTe Embodiment

FIG. 26 is a cross-section through an externally-gripping casing running tool (CRTe) 1000 configured to grip a tubular workpiece 1001. CRTe 1000 comprises:

-   -   a variable length axial linkage 1100 in accordance with         International Application No. PCT/CA2021/000096 (Slack) [the         contents of which are incorporated herein in their entirety];     -   an embodiment 1200 of a latch release mechanism in accordance         with the present disclosure;     -   a main body assembly 1300 having a main body bore 1301; and     -   a grip assembly 1400 coaxially disposed within the main body         bore 1301 of main body assembly 1300.

FIG. 27 is a front elevation of variable-length axial linkage 1100 and latch release mechanism 1200 of CRTe 1000. FIG. 28 is an isometric view of variable-length axial linkage 1100 and latch release mechanism 1200 with latch release mechanism 1200 exploded.

Variable-length axial linkage 1100 comprises a drive cam body 1110, an intermediate cam body 1120, a driven cam body 1130, a latch body 1140, a striker body 1150, and a striker spring 1160. Drive cam body 1110 comprises:

-   -   a load adaptor 1111 for connecting CRTe 1000 to a top drive         quill of a top-drive-equipped drilling rig (not shown); and     -   a plurality of downward-facing trigger reaction dog pockets         1113.         Latch release mechanism 1200 comprises a trigger element 1210, a         bumper element 1220, a plurality of trigger followers 1230, a         cage connector 1240, and a trigger spring 1250. Main body         assembly 1300 comprises a main body upper housing 1310, a main         body lower housing 1320, and a main body lock sleeve 1330. Grip         assembly 1400 comprises a cage 1410, a plurality of jaws 1420,         and a plurality of dies 1430.

Main body assembly 1300 is axially carried by drive cam body 1110. Main body upper housing 1310 is threadingly engageable with main body lower housing 1320, with main body lock sleeve 1330 preventing relative rotation between main body upper housing 1310 and main body lower housing 1320.

Each die 1430 has a grip surface configured for engagement with tubular workpiece 1001. Cage connector 1240 is rigidly coupled to both driven cam body 1130 and cage 1410. Extension of variable-length axial linkage 1100 causes downward movement of grip assembly 1400 relative to main body assembly 1300, and causes jaws 1420 and dies 1430 to move radially inward to engage tubular workpiece 1001.

An upper latch assembly 1010 of CRTe 1000 comprises a drive cam body 1110. A lower latch assembly 1020 of CRTe 1000 comprises an intermediate cam body 1120, a driven cam body 1130, a latch body 1140, a striker body 1150, and a striker spring 1160. Variable-length axial linkage 1100 has an internal latch that is operable between a latched position and an unlatched position in response to application of relative rotation, and an associated torque, between upper latch assembly 1010 and lower latch assembly 1020 in a first rotational direction. In the latched position, relative axial separation of upper latch assembly 1010 and lower latch assembly 1020 is constrained. In the unlatched position, relative axial separation of upper latch assembly 1010 and lower latch assembly 1020 is permitted within a defined range for operation of CRTe 1000. A gas spring 1030 formed within main body bore 1301 of main body assembly 1300 acts to urge axial separation of upper latch assembly 1010 and lower latch assembly 1020, and thus to urge engagement of dies 1430 with tubular workpiece 1001.

Trigger element 1210, bumper element 1220, and cage connector 1240 are generally cylindrical and coaxially nested. Trigger element 1210 is coupled to bumper element 1220 by a spline so as to be axially movable relative to bumper element 1220. Trigger spring 1250 acts between trigger element 1210 and bumper element 1220 to axially urge trigger element 1210 toward drive cam body 1110, and thus bias trigger dog teeth 1212 toward engagement with trigger reaction dog pockets 1113. Trigger spring 1250 urges bumper element 1220 axially away from trigger element 1210 and thus, away from axial linkage 1100. Trigger followers 1230 are rigidly mounted to cage connector 1240. Trigger followers 1230 also are slidingly disposed within corresponding bumper cam slots 1222 in bumper element 1220. Bumper cam slots 1222 are configured such that when bumper element 1220 moves axially relative to cage connector 1240, bumper element 1220 will also rotate relative to cage connector 1240. Trigger followers 1230 also are disposed within corresponding trigger pockets 1212 in trigger element 1210 such that trigger element 1210 is axially and rotationally movable relative to cage connector 1240 within a range defined by trigger pockets 1212.

Operation of the Latch Release Mechanism

Latch release mechanism 1200 is configured such that when trigger dog teeth 1212 are disposed within trigger reaction dog pockets 1113, an axial force applied to bumper element 1220 by tubular workpiece 1001 will tend to cause axial stroking of bumper element 1220 relative to lower latch assembly 1020 so as to urge relative rotation between upper latch assembly 1010 and lower latch assembly 1020 so as to move variable-length axial linkage 1100 from the latched position to an unlatched position with the associated torque transmitted through trigger element 1210; and such that application of additional axial force and the resultant axial and rotational displacement of bumper element 1220 relative to lower latch assembly 1020 will cause withdrawal of trigger dog teeth 1212 from trigger reaction dog pockets 1113.

FIGS. 29A, 29B, 30A, 30B, 31A, 31B, 32A, and 32B show variable-length axial linkage 1100 and latch release mechanism 1200 with trigger spring 1250 hidden and the lower portion of drive cam body 1110 cut away to reveal trigger dog teeth 1212 and trigger reaction dog pockets 1113. FIGS. 29A, 30A, 31A, and 32A are cross-sections through variable-length axial linkage 1100 and latch release mechanism 1200. FIGS. 29B, 30B, 31B, and 32B are front elevations of variable-length axial linkage 1100 and latch release mechanism 1200 with driven cam body 1130 and cage extension 1240 sectioned to reveal trigger element 1210 and bumper element 1220.

FIGS. 29A and 29B show variable-length axial linkage 1100 in the latched position. When CRTe 1000 is lowered onto tubular workpiece 1001 by a top drive of a drilling rig, tubular workpiece 1001 applies an axial force to bumper element 1220 tending to compressively stroke latch release mechanism 1200. Axial movement of bumper element 1220 relative to cage connector 1240 causes bumper element 1220 and trigger element 1210 to rotate relative to cage connector 1240 through the movement of trigger followers 1230 within bumper cam slots 1222. Stroking of latch release mechanism 1200 thus urges relative rotation between upper latch assembly 1010 and lower latch assembly 1020, with the associated torque transmitted through trigger element 1210 to upper latch assembly 1010 and through cage connector 1240 to lower latch assembly 1020.

FIGS. 30A and 30B show latch release mechanism 1200 stroked sufficiently to move variable-length axial linkage 1100 to an unlatched position. Application of additional axial force on bumper element 1220 by tubular workpiece 1001 and continued stroking of latch release mechanism 1200 causes further axial and rotational displacement of bumper element 1220 relative to cage connector 1240 and lower latch assembly 1020. This further axial and rotational displacement causes withdrawal of trigger dog teeth 1212 from trigger reaction dog pockets 1113 through the action of trigger followers 1230 within trigger pockets 1212 and bumper cam slots 1222. FIGS. 31A and 31B show latch release mechanism 1200 fully stroked to retract trigger dog teeth 1213 from trigger reaction dog pockets 1113.

Variable-length axial linkage 1100 may be relatched by operating CRTe 1000 to apply compressive axial load to variable-length axial linkage 1100 and to rotate upper latch assembly 1010 relative to lower latch assembly 1020 to return variable-length axial linkage 1100 to the latched position. FIGS. 32A and 32B show variable-length axial linkage 1100 returned to the latched position. Trigger dog teeth 1213 are still retracted from trigger reaction dog pockets 1113.

With variable-length axial linkage 1100 relatched, CRTe 1000 does not grip tubular workpiece 1001. When CRTe 1000 is raised away from tubular workpiece 1001 by the drilling rig, trigger spring 1250 acts between trigger element 1210 and bumper element 1220 to urge trigger element 1210 toward drive cam body 1110, and thus biasing trigger dog teeth 1212 toward engagement with trigger reaction dog pockets 1113. Trigger bumper spring 1250 simultaneously urges bumper element 1220 axially away from trigger element 1210 and therefore away from axial linkage 1100. Bumper element 1220 will move axially relative to cage connector 1240, and the action of trigger followers 1230 within bumper cam slots 1222 will rotate bumper element 1220 and trigger element 1210 to align trigger dog teeth 1213 with trigger reaction dog pockets 1113, thus resetting latch release mechanism 1200 to the initial state shown in FIGS. 29A and 29B.

It will be readily appreciated by those skilled in the art that various alternative embodiments may be devised without departing from the scope of the present teachings, including modifications that may use equivalent structures or materials subsequently conceived or developed.

It is to be especially understood that it is not intended for apparatus in accordance with the present disclosure to be limited to any described or illustrated embodiment, and that the substitution of a variant of a claimed element or feature, without any substantial resultant change in the working of the apparatus and methods, will not constitute a departure from the scope of the disclosure.

In this patent document, any form of the word “comprise” is to be understood in its non-limiting sense to mean that any element or feature following such word is included, but elements or features not specifically mentioned are not excluded. A reference to an element or feature by the indefinite article “a” does not exclude the possibility that more than one of such element or feature is present, unless the context clearly requires that there be one and only one such element or feature.

Any use of any form of the terms “connect”, “engage”, “couple”, “latch”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure.

Relational and conformational terms such as (but not limited to) “vertical”, “horizontal”, “coaxial”, “cylindrical”, “trapezoidal”, “upward-facing”, and “downward-facing” are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring substantial precision only (e.g., “substantially “vertical” or “generally trapezoidal”) unless the context clearly requires otherwise.

In particular, it is to be understood that any reference herein to an element as being “generally cylindrical” is intended to mean that the element in question may have inner and outer diameters that vary along the length of the element.

Wherever used in this document, the terms “typical” and “typically” are to be understood and interpreted in the sense of being representative of exemplary common usage or practice only, and are not to be understood or interpreted as implying essentiality or invariability.

LIST OF ILLUSTRATED ELEMENTS Element Number Description 100 (prior art) CRT 101 tubular workpiece 102 (tubular workpiece) threaded coupling 110 body assembly 111 load adapter 112 tapered-thread connection 120 grip assembly 121 bumper 122 land surface 123 jaws 130 CRTi 131 latch release mechanism 132 tri-cam latching linkage 133 upper latch assembly 134 lower latch assembly 135 (prior art) CRTi 136 latch release mechanism 140 (prior art) CRTe 150 main body assembly 151 main body upper housing 152 main body lower housing 153 upper housing lock surface 154 axial shoulder 160 floating load adaptor 161 upper axial shoulder 162 lower axial shoulder 163 load adaptor extension 164 lug 165 skirt 170 grip assembly 171 bumper 172 land surface 180 tri-cam latching linkage 181 upper latch assembly 182 axial shoulder 183 lower latch assembly 184 drive cam 185 drive cam latch hooks 186 drive cam housing 187 driven cam 188 latch cam 189 latch cam latch hooks 190 upper cam-housing seal 191 main body-housing upper seal 192 lower cam-housing seal 193 main body-housing lower seal 194 lower cam-cage seal 195 upper cam-cage seal 196 gas spring chamber 197 CRTe (with latch release mechanism) 198 latch release mechanism 201 latch release mechanism 204 trigger reaction ring 205 trigger reaction dog pocket 206 reaction pocket load flank 207 reaction pocket crest 208 reaction pocket lock flank 210 trigger element 211 trigger dog tooth/teeth 212 trigger dog tooth load flank 213 trigger dog tooth crest 214 trigger dog tooth lock flank 218 movable bumper 220 movable land surface 222 cage extension 301 upper latch assembly 302 upper rotary latch receiver 303 internal upper cam ramp surface 304 internal lower cam ramp surface 305 internal biasing spring 310 lower latch assembly 312 lower rotary latch hook 314 bumper-trigger cam follower 315 bumper-trigger cam slot 316 (bumper-trigger cam slot) upper end 317 (bumper-trigger cam slot) lower end 318 bumper-cage cam follower 319 bumper-cage cam slot 320 (bumper-cage cam slot) upper end 321 (bumper-cage cam slot) lower end 322 trigger-cage cam follower 324 trigger-cage cam pocket 326 trigger bias spring 330 trigger advance cam surface 332 trigger withdraw cam surface 334 trigger re-latch cam surface 336 trigger reset cam surface 400 drive cam body 401 drive cam latch hooks 402 load threads 403 drive cam body-housing seal 404 drive cam body-mandrel seal 410 trigger reaction ring 411 trigger reaction dog pocket 412 reaction pocket load flank 413 reaction pocket crest 414 reaction pocket lock flank 420 drive cam housing 421 drive housing-driven housing seal 422 gas spring chamber 430 intermediate cam body 431 load threads 440 trigger element 441 trigger dog tooth/teeth 442 trigger dog tooth load flank 443 trigger dog tooth crest 444 trigger dog tooth lock flank 445 trigger cam slot 446 (trigger cam slot) upper end 447 (trigger cam slot) lower end 448 trigger cam follower 449 trigger bias spring 450 movable bumper 451 movable land surface 452 bumper cam follower 460 cage extension 461 bumper-cage cam slot 462 (bumper-cage cam slot) upper end 463 (bumper-cage cam slot) lower end 464 cage cam pocket 466 advance cam surface 467 withdraw cam surface 469 reset cam surface 470 driven cam body 472 drive cam body-cage seal 480 driven cam housing 490 latch cam 491 latch cam latch hooks 500 cage 501 cage mandrel seal 510 cage extension 511 cage cam slot 512 (cage cam slot) upper end 513 (cage cam slot) lower end 520 trigger bias spring 600 primary trigger (alternatively referred to as primary trigger element) 601 load adapter cam follower 602 primary trigger dog tooth/teeth 603 primary trigger dog tooth load flank 604 primary trigger dog tooth crest 605 primary trigger dog tooth lock flank 606 primary trigger cam slot 607 (primary trigger cam slot) upper portion 608 (primary trigger cam slot) lower portion 612 dog retraction cam slot 613 (dog retraction cam slot) upper end 614 (dog retraction cam slot) lower end 615 downward-facing primary trigger reaction surface 618 trigger bias spring 620 secondary trigger (alternatively referred to as secondary trigger element) 621 secondary trigger cam slot 622 (secondary trigger cam slot) upper end 623 (secondary trigger cam slot) lower end 624 secondary trigger cam follower 625 secondary trigger thread 630 secondary trigger extension 631 standoff surface (lower end of secondary trigger extension) 632 secondary trigger extension thread 633 secondary trigger extension lug 640 main body extension 641 second reaction surface 642 reaction dog pocket 643 reaction pocket load flank 644 reaction pocket crest 645 reaction pocket lock flank 646 dog reaction surface (alternatively referred to as first reaction surface) 647 axially-oriented slots 648 main body extension load shoulder 649 main body extension lock surface 650 clamp ring 651 clamp ring load shoulder 660 main body lock 661 main body lock lugs 1000 externally-gripping casing running tool (CRTe) 1001 tubular workpiece 1010 upper latch assembly 1020 lower latch assembly 1030 gas spring 1100 variable-length axial linkage 1110 drive cam body 1111 load adaptor 1113 trigger reaction dog pockets 1120 intermediate cam body 1130 lower cam body 1140 latch body 1150 striker body 1160 striker spring 1200 latch release mechanism 1210 trigger element 1211 trigger spline 1212 trigger pocket 1213 trigger dog teeth 1220 bumper element 1221 bumper spline 1222 bumper cam slot 1230 trigger follower 1240 cage connector 1250 trigger spring 1300 main body assembly 1301 main body bore 1310 main body upper housing 1320 main body lower housing 1330 main body lock sleeve 1400 grip assembly 1410 cage 1420 jaws 

What is claimed is:
 1. A latch release mechanism having a longitudinal axis and acting between an upper latch assembly and a lower latch assembly, said upper and lower latch assemblies being coaxially aligned with the latch release mechanism, and wherein: (a) the upper and lower latch assemblies are operable between: a latched position, in which relative axial separation of the upper and lower latch assemblies is constrained; and an unlatched position, in which relative axial motion of the upper and lower latch assemblies is permitted within a defined range;  in response to application of relative rotation, and an associated torque, between the upper and lower latch assemblies in a first rotational direction; (b) the upper latch assembly defines one or more trigger reaction dog pockets; and (c) the upper latch assembly axially carries a generally cylindrical main body assembly having a main body bore; wherein the latch release mechanism is coaxially disposed within the main body bore and comprises: (d) a bumper element coupled to the lower latch assembly, such that when the bumper element is moved axially relative to the lower latch assembly, the bumper element will also rotate relative to the lower latch assembly; and (e) a trigger element coupled to the bumper element and the lower latch assembly so as to be at least axially movable relative to the bumper element, and so as to be axially and rotationally movable relative to the lower latch assembly within a defined range, wherein the trigger element defines one or more trigger dog teeth configured for axial engagement and disengagement with the one or more trigger reaction dog pockets of the upper latch assembly; such that when the one or more trigger dog teeth are disposed within the one or more trigger reaction dog pockets: application of an axial force to the bumper element will tend to cause axial stroking of the bumper element relative to the lower latch assembly so as to urge relative rotation between the upper and lower latch assemblies in the first rotational direction to move the upper and lower latch assemblies from the latched position to the unlatched position with the associated torque transmitted through the trigger element; and application of additional axial force and the resultant axial and rotational displacement of the bumper element relative to the lower latch assembly will cause withdrawal of the one or more trigger dog teeth from the one or more trigger reaction dog pockets.
 2. The latch release mechanism as in claim 1, wherein the bumper element and the trigger element are configured as a coaxially-nested group of closely-fitting generally cylindrical components.
 3. The latch release mechanism as in claim 2, wherein the bumper element is axially movable relative to the trigger element by means of a spline coupling.
 4. The latch release mechanism as in claim 1, further comprising a trigger follower coupled to the lower latch assembly and movably disposed within a trigger pocket formed in the trigger element, such that the range of axial and rotational movement of the trigger element relative to the lower latch assembly is defined by the configuration of said trigger pocket.
 5. The latch release mechanism as in claim 4, wherein the trigger follower is also movably disposed within a bumper cam slot formed in the bumper element, such that the range of axial and rotational movement of the bumper element relative to the lower latch assembly is defined by the configuration of the bumper cam slot.
 6. The latch release mechanism as in claim 1, further comprising a bumper follower coupled to the lower latch assembly and movably disposed within a bumper cam slot formed in the bumper element, such that the range of axial and rotational movement of the bumper element relative to the lower latch assembly is defined by the configuration of the bumper cam slot.
 7. The latch release mechanism as in claim 5, wherein the bumper cam slot is configured as an elongate slot having a slope relative to the longitudinal axis of the latch release mechanism.
 8. The latch release mechanism as in claim 7, wherein the slope of the bumper cam slot relative t the longitudinal axis varies along the length of the bumper cam slot.
 9. The latch release mechanism as in claim 1, further comprising a trigger biasing means urging the trigger element axially upward toward the upper latch assembly and thus urging the one or more trigger dog teeth toward engagement with the one or more trigger reaction dog pockets.
 10. The latch release mechanism as in claim 9, wherein the trigger biasing means acts between the trigger element and the bumper element so as to urge the bumper element axially downward away from the trigger element.
 11. The latch release mechanism as in claim 1, further comprising a bumper biasing means urging the bumper element axially downward away from the trigger element.
 12. The latch release mechanism as in claim 1, wherein the upper latch assembly is coupled to a top drive quill of a top-drive-equipped drilling rig, and the lower latch assembly is coupled to a grip assembly of a casing running tool coaxially disposed within the main body bore. 